QUESTIONS AND ANSWERS

        The following are some questions that you, as a stockholder of AECOM Technology Corporation, a Delaware corporation ("AECOM"), or URS Corporation, a Delaware corporation ("URS"), may have regarding the merger and the other matters being considered at the special meetings and the answers to those questions. AECOM and URS urge you to carefully read the remainder of this joint proxy statement/prospectus because the information in this section does not provide all the information that might be important to you with respect to the merger and the other matters being considered at the special meetings. Additional important information is also contained in the Annexes to, and the documents incorporated by reference into, this joint proxy statement/prospectus.

Q:

Why am I receiving this joint proxy statement/prospectus?

A:

AECOM and its newly formed, direct wholly owned subsidiaries, ACM Mountain I, LLC ("Merger Sub") and ACM Mountain II, LLC ("Merger Sub I"), have entered into an Agreement and Plan of Merger, dated as of July 11, 2014 (as it may be amended from time to time, the "merger agreement"), with URS. Subject to the terms and conditions of the merger agreement, at the effective time of the merger, Merger Sub will be merged with and into URS, with URS surviving the merger as a wholly owned subsidiary of AECOM (the "merger"). At the effective time of the second merger, which will be immediately following the merger, and as part of a single integrated transaction with the merger, URS will be merged with and into Merger Sub I, with Merger Sub I surviving the second merger as a limited liability company and a wholly owned subsidiary of AECOM (the "second merger" and, together with the merger, the "mergers"). There are no conditions to the second merger other than consummation of the merger. A copy of the merger agreement is included in this joint proxy statement/prospectus as Annex A.

The merger cannot be completed unless, among other things:

•

holders of a majority of the shares of AECOM common stock present in person or represented by proxy at the AECOM special meeting vote to approve the issuance of shares of AECOM common stock in connection with the merger pursuant to the merger agreement (the "stock issuance"); and

•

holders of a majority of the shares of the outstanding URS common stock as of the record date for the URS special meeting vote to adopt the merger agreement.

In addition, AECOM is soliciting proxies from its stockholders with respect to one additional proposal; completion of the merger is not conditioned upon receipt of this approval:

•

a proposal to adjourn the AECOM special meeting, if necessary or appropriate, to solicit additional proxies in favor of the stock issuance if there are insufficient votes at the time of such adjournment to approve such proposal (the "AECOM adjournment proposal").

Furthermore, URS is soliciting proxies from its stockholders with respect to two additional proposals; completion of the merger is not conditioned upon receipt of these approvals:

•

a proposal to adjourn the URS special meeting, if necessary or appropriate, to solicit additional proxies in favor of the proposal to adopt the merger agreement if there are insufficient votes at the time of such adjournment to approve such proposal (the "URS adjournment proposal"); and



•

a proposal to approve, on an advisory (nonbinding) basis, the compensation that may be paid or become payable to URS's named executive officers in connection with the merger, and the agreements and understandings pursuant to which such compensation may be paid or become payable (the "golden parachute proposal").

Each of AECOM and URS will hold separate special meetings to obtain these approvals (the "AECOM special meeting" and the "URS special meeting," respectively). This joint proxy statement/prospectus contains important information about the merger and the other proposals being voted on at the special meetings, and you should read it carefully. It is a joint proxy statement because both the AECOM and URS boards of directors are soliciting proxies from their respective stockholders. It is a prospectus because AECOM will issue shares of AECOM common stock in connection with the merger. The enclosed materials allow you to have your shares voted by proxy without attending your respective meeting. Your vote is important. We encourage you to submit your proxy as soon as possible.

Q:

What will I receive in the merger in exchange for my shares of common stock?

A:

AECOM Stockholders:    If the merger is completed, AECOM stockholders will not receive any merger consideration and will continue to hold the shares of AECOM common stock which they currently hold. Following the merger, shares of AECOM common stock will continue to be traded on the New York Stock Exchange (the "NYSE") under the symbol "ACM."

URS Stockholders:    If the merger is completed, URS stockholders will be entitled to receive, in exchange for each share of URS common stock they hold at the effective time of the merger, either stock or cash consideration with a value equal to the sum of (i) 0.734 multiplied by the average (rounded to the nearest one tenth of a cent) of the closing sales prices on the NYSE for AECOM common stock during the five trading days ending the day before the completion of the merger (the "average five-day AECOM closing price") and (ii) $33.00. URS stockholders will have the right to elect to receive merger consideration for each of their shares of URS common stock in the form of cash or shares of AECOM common stock, subject to proration in the circumstances described below. In the event of proration, a URS stockholder may receive a portion of the merger consideration in a form other than that which such stockholder elected.

The value of the merger consideration will fluctuate with the market price of the AECOM common stock and will be determined based on the average five-day AECOM closing price. We urge you to obtain current market quotations of shares of AECOM and URS common stock. As explained in more detail in this joint proxy statement/prospectus, whether a URS stockholder makes a cash election or a stock election, the value of the consideration that such stockholder receives as of the date of completion of the merger will be approximately equivalent based on the average five-day AECOM closing price used to calculate the merger consideration. A URS stockholder may specify different elections with respect to different shares that such stockholder holds (e.g., if a URS stockholder owns 100 shares of URS common stock, that stockholder could make a cash election with respect to 50 shares and a stock election with respect to the other 50 shares).

The aggregate amount of cash to be paid to holders of URS common stock (not including, for this purpose, URS election award shares (as defined below)) as of immediately prior to closing is fixed in the merger agreement at $2,257,950,321. As a result, if the cash election is oversubscribed or undersubscribed, then certain adjustments will be made to the merger consideration to proportionately reduce the cash or stock amounts received by the URS stockholders in the manner described below in the section entitled "The Merger Agreement—Consideration to Be Received in the Merger—Proration." To the extent that the number of outstanding shares of URS increases between the date of the merger agreement and the effective time of the merger, due to the vesting of stock-settled awards or as otherwise permitted by the merger agreement, the aggregate number of shares of AECOM common stock to be issued as consideration in the merger will be increased accordingly, but the aggregate amount of cash to be paid as consideration to holders of URS common stock will not change. In addition, if the aggregate consideration to be paid to any holder

of URS common stock would result in such holder receiving a fractional share of AECOM common stock, cash will be paid in lieu of such fractional share.

As an example, based on the average (rounded to the nearest one tenth of a cent) of the closing sales prices of AECOM common stock for the five trading days ending on July 11, 2014 (the last trading date before announcement of the merger), for each share of URS common stock held, a URS stockholder would receive either approximately $56.41 in cash or 1.7687 shares of AECOM common stock, subject to proration if cash was oversubscribed or undersubscribed. As another example, based on the average (rounded to the nearest one tenth of a cent) of the closing sales prices of AECOM common stock for the five trading days ending on September 12, 2014 (the most recent practicable trading date before filing of this joint proxy statement/prospectus), for each share of URS common stock held, a URS stockholder would receive either approximately $60.44 in cash or 1.6166 shares of AECOM common stock, subject to proration if cash was oversubscribed or undersubscribed.

The exact amount of cash and number of shares of AECOM common stock you receive will depend on the election you and other holders of URS common stock make and the formula in the merger agreement, including its election, proration and adjustment provisions. For a summary of the formula contained in the merger agreement, see "The Merger Agreement—Consideration to be Received in the Merger."

Q:

What will I receive in the merger in exchange for my equity awards?

A:

AECOM Stockholders:    If the merger is completed, holders of AECOM equity awards will not receive any merger consideration and will continue to hold the AECOM equity awards that they currently hold.

URS Stockholders:    If the merger is completed, certain URS equity awards ("URS roll-over award shares") will be assumed by AECOM and converted into AECOM equity awards as follows:

•

Certain URS Time Vesting Restricted Stock Units and Restricted Stock Awards.  Upon consummation of the merger, each outstanding and unvested URS restricted stock unit and URS restricted stock award that vests solely based on the passage of time and that does not vest by its terms upon the consummation of the merger will be assumed by AECOM and converted into restricted stock and restricted stock units with respect to whole shares of AECOM common stock, on the same terms and conditions as applied to such URS restricted stock unit and URS restricted stock awards immediately prior to the consummation of the merger, with the number of shares of AECOM common stock subject to each such assumed share of restricted stock and restricted stock unit determined based upon the exchange ratio, which is the quotient, rounded to the nearest one ten thousandth, obtained by dividing the per share cash amount (which is the amount obtained by adding (i) $33.00 and (ii) the product of 0.734 times the average five-day AECOM closing price) by the average five-day AECOM closing price. Any corresponding accrued but unpaid dividends and dividend equivalents with respect to such URS restricted stock units and URS restricted stock awards will also be assumed by AECOM and remain outstanding as an obligation with respect to the converted award.

In addition, if the merger is completed, holders of certain other URS equity awards ("URS election award shares") will have the right to elect to receive merger consideration in the form of cash or shares of AECOM common stock, subject to proration in the circumstances described in the enclosed joint proxy statement/prospectus:

•

Certain URS Time Vesting Restricted Stock Units and Restricted Stock Awards.  Immediately prior to the consummation of the merger, each outstanding URS restricted stock unit and URS restricted stock award that vests solely based on the passage of time and that either is vested,

but not yet settled at the time the merger is consummated, or that vests by its terms upon the consummation of the merger will immediately and automatically vest and entitle the holder thereof to the merger consideration, subject to proration, and the holder will be entitled to any corresponding accrued but unpaid dividends or dividend equivalents (less applicable withholding), which will be paid and/or delivered, as applicable, within thirty (30) days after the closing date, subject to certain limited exceptions.

•

Performance Vesting Restricted Stock Units and Restricted Stock Awards.  Immediately prior to the consummation of the merger, each outstanding URS restricted stock unit and URS restricted stock award that vests, in whole or in part, based on the achievement of performance goals (other than the performance-based awards granted in March 2013 with a two-year performance period ending January 2, 2015, which will only vest if the applicable performance goal is determined to be achieved measured as of the month-end prior to the effective time), will immediately and automatically vest based on the deemed achievement of the performance goals at target level and entitle the holder thereof to the merger consideration, subject to proration, and the holder will be entitled to any corresponding accrued but unpaid dividends or dividend equivalents (less applicable withholding), which will be paid and/or delivered, as applicable, within forty-five (45) days after the closing date, subject to certain limited exceptions.



•

Deferred Stock Units and Deferred Restricted Stock Units.  Upon consummation of the merger, each outstanding URS deferred stock award held by a non-employee director and each outstanding URS deferred restricted stock unit, all of which are vested, will entitle the holder thereof to the merger consideration, subject to proration. The delivery and/or payment, as applicable, of the merger consideration and any dividend equivalents will be made on the first business day that follows the six (6) month anniversary of the holder's separation from service with URS and AECOM, subject to certain limited exceptions.

Based upon 1,591,993 outstanding URS election award shares on the record date for the URS special meeting, AECOM will issue an aggregate of 1,168,503 shares of AECOM common stock to holders of URS election award shares as of immediately prior to closing in connection with the merger, will pay an aggregate cash consideration of $52,535,769 to holders of URS election award shares as of immediately prior to closing in connection with the merger and will reserve an aggregate of 2,200,458 shares of AECOM common stock in respect of AECOM equity awards issued to holders of URS roll-over award shares as of immediately prior to the closing in connection with the merger (the "URS equity award merger consideration"), although these numbers may change based on the number of outstanding URS equity awards on the closing date. See "The Merger Agreement—Consideration to be Received in the Merger."

Q:

What are the details of the consideration election?

A:

You will be allowed to make a cash election with respect to any or all of your shares of URS common stock and/or a stock election with respect to any or all of your other shares of URS common stock (subject to proration if cash is oversubscribed or undersubscribed):

•

A cash election with respect to a share of URS common stock means a request to receive cash in the amount (the "per share cash amount") of (1) $33.00 plus (2) the product, rounded to the nearest one tenth of a cent, of 0.734 multiplied by the average, rounded to the nearest one tenth of a cent, of the average five-day AECOM closing price.

•

A stock election with respect to a share of URS common stock means a request to receive that number of shares of AECOM common stock equal to (1) the per share cash amount divided by (2) the average five-day AECOM closing price.

The exact amount of cash and number of shares of AECOM common stock you receive will depend on the election you and other URS stockholders make and the formula in the merger agreement, including its election, proration and adjustment provisions. In addition, if the aggregate consideration to be paid to any holder of URS common stock would result in such holder receiving a fractional share of AECOM common stock, cash will be paid in lieu of such fractional share. For a summary of the formula contained in the merger agreement, see "The Merger Agreement—Consideration to be Received in the Merger."

Q:

How do I make an election?

A:

If you are the record holder of shares of URS common stock on September 12, 2014, the record date for the URS special meeting (the "URS record date"), you will receive an election form enclosed with this joint proxy statement/prospectus (the "election form") specifying the number of shares of URS common stock, if any, you desire to convert into the right to receive merger consideration in the form of cash or shares of AECOM common stock. You must deliver a completed election form by 2:00 p.m., California time, on October 15, 2014 (the "election deadline"), to Computershare Trust Company, N.A., as exchange agent (whom we refer to as the "exchange agent"). Such election form must be accompanied by the certificates representing the shares of URS common stock (or guarantee of delivery), unless such shares are in book-entry form ("book-entry shares"), in which case you should follow the instructions set forth in the election form. If you hold your shares of URS common stock through a bank, broker or other nominee, your bank, broker or other nominee, as applicable, will provide you with instructions on how to make an election. If your election form is received after the election deadline or you fail to comply with your bank's, broker's or nominee's instructions, your election will be disregarded, and you will receive consideration in whatever form or mix that remains after taking into account other URS stockholders' preferences.

If you hold URS election award shares (including restricted stock), URS will provide you with separate instructions on how to make an election.

If you hold shares of URS common stock through a URS Corporation 401(k) Retirement Plan account, you will receive separate instructions on how to make an election with respect to such shares.

Q:

How can I change my election?

A:

If you are a record holder of URS common stock, you may (i) change your election by written notice received by the exchange agent prior to the election deadline, accompanied by a properly completed and signed revised election form or (ii) revoke your election by written notice received by the exchange agent prior to the election deadline or by withdrawal, prior to the election deadline, of the certificates representing your shares of URS common stock, or of the guarantee of delivery of such certificates, previously deposited with the exchange agent. If your election form is revoked, the certificate(s) (or guarantees of delivery, as appropriate), if any, for the shares of URS common stock to which such election form relates will be promptly returned to you.

If you hold URS election award shares (including restricted stock), URS will provide you with separate instructions on how to make or change your election.

Q:

Am I required to make an election in order to receive the merger consideration?

A:

No. If you do not make an election, you will still receive the merger consideration upon completion of a duly executed letter of transmittal and delivery of your stock certificates (or book-entry shares). However, if you have a preference for a specific form of merger consideration and do not make an election, the exchange agent will not take your preference into consideration.

If you do not make an election, you will receive the merger consideration in whatever form or mix remains after giving effect to the preferences of the URS stockholders that do make elections. If the cash election is oversubscribed, you will receive shares of AECOM common stock; if the cash election option is undersubscribed, you will receive cash consideration.

Q:

When and where will the special meetings be held?

A:

AECOM Stockholders:    The AECOM special meeting will be held at AECOM's headquarters located at 1999 Avenue of the Stars, Suite 2600, Los Angeles, California 90067, on October 16, 2014, at 8:30 a.m., California time.

URS Stockholders:    The URS special meeting will be held at 600 Montgomery Street, 26th Floor, San Francisco, California 94111, on October 16, 2014, at 10:00 a.m., California time.

Q:

What are the proposals on which I am being asked to vote?

A:

AECOM Stockholders:    AECOM is soliciting proxies from its stockholders with respect to two proposals:

•

the stock issuance proposal, approval of which is a condition to completion of the merger; and

•

the AECOM adjournment proposal, approval of which is not a condition to completion of the merger.

URS Stockholders:    URS is soliciting proxies from its stockholders with respect to three proposals:

•

a proposal to adopt the merger agreement, approval of which is a condition to completion of the merger;

•

the URS adjournment proposal, approval of which is not a condition to completion of the merger; and

•

the golden parachute proposal, approval of which is not a condition to completion of the merger.

Q:

What constitutes a quorum at the meetings?

A:

AECOM Stockholders:    Stockholders who hold a majority of the shares of AECOM common stock outstanding on September 12, 2014, the record date for the AECOM special meeting (the "AECOM record date"), and who are entitled to vote must be present in person or represented by proxy to constitute a quorum at the AECOM special meeting. Subject to consultation with URS pursuant to the terms of the merger agreement, the AECOM stockholders, by a majority vote at the meeting by the holders of AECOM common stock entitled to vote and present in person or represented by proxy, whether or not a quorum is present, may adjourn the meeting to another time or place without further notice. If the adjournment is for more than 30 days or, if after the adjournment, a new record date is fixed for the adjourned meeting, a new notice of the adjourned meeting will be given to each stockholder of record entitled to vote at the adjourned meeting.

Failures to vote will not be included in the calculation of the number of shares of AECOM common stock represented at the AECOM special meeting for purposes of determining whether a quorum has been achieved. Abstentions will be included in the calculation of the number of shares of AECOM common stock represented at the AECOM special meeting for purposes of determining whether a quorum has been achieved. Under NYSE rules, if brokers do not have discretion to vote on any of the proposals at a stockholders' meeting, broker non-votes will not count toward the calculation of a quorum. As each of the proposals to be voted on at the AECOM special meeting is considered "non-routine" under NYSE rules, brokers do not have

discretion to vote on such proposals and, as such, broker non-votes will not be included in the calculation of the number of shares of AECOM common stock represented at the AECOM special meeting for purposes of determining whether a quorum has been achieved.

URS Stockholders:    Stockholders who hold shares representing at least a majority of the outstanding shares of URS common stock entitled to vote at the URS special meeting must be present in person or represented by proxy to constitute a quorum for the transaction of business at the URS special meeting. Subject to consultation with AECOM pursuant to the terms of the merger agreement, the URS stockholders, by a majority vote at the meeting by the holders of URS common stock entitled to vote and present in person or represented by proxy, whether or not a quorum is present, may adjourn the meeting to another time or place without further notice. If the adjournment is for more than 30 days or, if after the adjournment, a new record date is fixed for the adjourned meeting, a new notice of the adjourned meeting will be given to each stockholder of record entitled to vote at the adjourned meeting.

Failures to vote will not be included in the calculation of the number of shares of URS common stock represented at the URS special meeting for purposes of determining whether a quorum has been achieved. Abstentions will be included in the calculation of the number of shares of URS common stock represented at the URS special meeting for purposes of determining whether a quorum has been achieved. Under NYSE rules, if brokers do not have discretion to vote on any of the proposals at a stockholders' meeting, broker non-votes will not count toward the calculation of a quorum. As each of the proposals to be voted on at the URS special meeting is considered "non-routine" under NYSE rules, brokers do not have discretion to vote on such proposals and, as such, broker non-votes will not be included in the calculation of the number of shares of URS common stock represented at the URS special meeting for purposes of determining whether a quorum has been achieved.

Q:

How do I vote?

A:

AECOM Stockholders:    If you are a stockholder of record of AECOM as of the close of business on the AECOM record date, you may vote in person by attending the AECOM special meeting or, to ensure your shares are represented at the AECOM special meeting, you may authorize a proxy to vote by:

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logging onto www.envisionreports.com/ACM and following the instructions on your proxy card to submit a proxy via the internet anytime up to 11:00 p.m., California time, on October 15, 2014, and following the instructions provided on that site;

•

dialing 800-652-8683 and listening for further directions to submit a proxy by telephone anytime up to 11:00 p.m., California time, on October 15, 2014, and following the instructions provided in the recorded message; or

•

signing and returning the accompanying proxy card in the enclosed postage-paid envelope. AECOM stockholders of record may submit their proxies through the mail by completing their proxy card and signing, dating and returning it in the enclosed, pre-addressed, postage-paid envelope. To be valid, a returned proxy card must be signed and dated.

URS Stockholders:    If you are a stockholder of record of URS as of the close of business on the URS record date, you may vote in person by attending the URS special meeting or, to ensure your shares are represented at the URS special meeting, you may authorize a proxy to vote by:

•

logging onto www.proxyvote.com and following the instructions on your proxy card to submit a proxy via the internet anytime up to 8:59 p.m., California time, on October 15, 2014, and following the instructions provided on that site;

•

dialing (800)-690-6903 and listening for further directions to submit a proxy by telephone anytime up to 8:59 p.m., California time, on October 15, 2014, and following the instructions provided in the recorded message; or



•

signing and returning the accompanying proxy card in the enclosed postage-paid envelope. URS stockholders of record may submit their proxies through the mail by signing, dating, completing and returning their proxy card in the enclosed, pre-addressed, postage-paid envelope. To be valid, a returned proxy card must be signed and dated.

If you hold shares of URS common stock through a URS Corporation 401(k) Retirement Plan account, you will receive separate instructions on how to vote such shares.

Q:

If my shares are held in a stock brokerage account, or in "street name" by my broker, bank or nominee, will my broker, bank or nominee automatically vote my shares for me?

A:

No. If you hold your shares in a stock brokerage account or if your shares are held by a bank or nominee (that is, in "street name"), you must provide the record holder of your shares with instructions on how to vote your shares. Please follow the voting instructions provided by your bank, broker or other nominee. Please note that you may not vote shares held in street name by returning a proxy card directly to AECOM or URS or by voting in person at your special meeting unless you provide a "legal proxy," which you must obtain from your bank, broker or other nominee. Further, brokers who hold shares of AECOM or URS common stock on behalf of their customers may not give a proxy to AECOM or URS to vote those shares without specific instructions from their customers.

Q:

What if I return my proxy card without indicating how to vote?

A:

If you sign and return your proxy card without indicating how to vote on any particular proposal, your shares will be voted in accordance with the recommendation of the AECOM or URS Board of Directors, as applicable, with respect to such proposal.

Q:

If I am a URS stockholder, should I send in my URS stock certificates with my proxy card?

A:

No. Please DO NOT send your URS stock certificates with your proxy card. You are being provided an election form and instructions regarding the surrender of your stock certificates. If you wish to make an election with respect to your shares of URS common stock, you should, prior to the election deadline, send your URS stock certificates (if any) to the exchange agent, together with your completed, signed election form.

Q:

How many votes do I have?

A:

AECOM Stockholders:    Holders of AECOM common stock are entitled to one vote for each share of AECOM common stock owned as of the AECOM record date. As of the close of business on the AECOM record date, there were 99,541,568 outstanding shares of AECOM common stock, approximately 2.03% of which were beneficially owned by the directors and executive officers of AECOM and their affiliates.

URS Stockholders:    Holders of URS common stock are entitled to one vote for each share of URS common stock owned as of the close of business on the URS record date. As of the close of business on the URS record date, there were 69,121,955 shares of URS common stock outstanding and entitled to vote at the URS special meeting, approximately 0.93% of which were beneficially owned by the directors and executive officers of URS and their affiliates.

Q:

What vote is required to approve each proposal?

A:

AECOM Stockholders:    Approval of the stock issuance proposal requires the affirmative vote of holders of the majority of shares of AECOM common stock present in person or represented by proxy at the AECOM special meeting and entitled to vote thereon, assuming a quorum is present, and is a condition to completion of the merger. Approval of the AECOM adjournment proposal requires the affirmative vote of the holders of a majority of the shares of AECOM common stock entitled to vote and present in person or represented by proxy at the AECOM special meeting, whether or not a quorum is present. Approval of the AECOM adjournment proposal is not a condition to completion of the merger.

URS Stockholders:    Adoption of the merger agreement requires the affirmative vote of the holders of a majority of the outstanding shares of URS common stock as of the URS record date, and is a condition to completion of the merger. Approval of the URS adjournment proposal requires the affirmative vote of the holders of a majority of the shares of URS common stock entitled to vote and present in person or represented by proxy at the URS special meeting, whether or not a quorum is present. Approval of the golden parachute proposal requires the affirmative vote of holders of the majority of shares of URS common stock present in person or represented by proxy at the URS special meeting and entitled to vote thereon, assuming a quorum is present. Neither approval of the URS adjournment proposal nor the golden parachute proposal is a condition to completion of the merger.

Q:

What will happen if I fail to vote or I abstain from voting?

A:

AECOM Stockholders:    If you are an AECOM stockholder and you fail to vote, it will have no effect on the AECOM adjournment proposal or, assuming a quorum is present, on the stock issuance proposal. If you abstain from voting, your shares will be counted as represented at the AECOM special meeting, and it will have the same effect as a vote "AGAINST" the stock issuance proposal and "AGAINST" the AECOM adjournment proposal.

URS Stockholders:    If you are a URS stockholder and you fail to vote, it will have the same effect as a vote "AGAINST" the proposal to adopt the merger agreement, but it will have no effect on the URS adjournment proposal or, assuming a quorum is present, on the golden parachute proposal. If you abstain from voting, your shares will be counted as represented at the URS special meeting, and it will have the same effect as a vote "AGAINST" the proposal to adopt the merger agreement, "AGAINST" the URS adjournment proposal and "AGAINST" the golden parachute proposal.

Q:

What will happen if I fail to instruct my broker, bank or nominee how to vote?

A:

AECOM Stockholders:    If you are an AECOM stockholder and you do not instruct your broker, bank or nominee on how to vote your shares, your broker may not vote your shares at the AECOM special meeting. This will have no effect on the AECOM adjournment proposal or, assuming a quorum is present, on the stock issuance proposal.

URS Stockholders:    If you are a URS stockholder and you do not instruct your broker, bank or nominee on how to vote your shares, your broker may not vote your shares at the URS special meeting. This will have the same effect as a vote "AGAINST" the adoption of the merger agreement, but will have no effect on the URS adjournment proposal or, assuming a quorum is present, on the golden parachute proposal.

Q:

Can I change my vote after I have returned a proxy or voting instruction card?

A:

AECOM Stockholders:    Yes. You can change your vote at any time before your proxy is voted at your special meeting. You can do this in one of three ways:

•

you can send a signed notice of revocation;

•

you can grant a new, valid proxy bearing a later date including by telephone or via the internet; or

•

if you are a holder of record, you can attend the AECOM special meeting and vote in person, which will automatically cancel any proxy previously given, or you may revoke your proxy in person, but your attendance alone will not revoke any proxy that you have previously given.

If you choose either of the first two methods, you must submit your notice of revocation or your new proxy to the Corporate Secretary of AECOM no later than the beginning of the AECOM special meeting. If you have submitted a proxy for your shares by telephone or via the internet, you may revoke your prior telephone or internet proxy by any manner described above. If your shares are held in street name by your broker, bank or nominee, you should contact your broker, bank or nominee to change your vote.

URS Stockholders:    Yes. You can change your vote at any time before your proxy is voted at your special meeting. You can do this in one of three ways:

•

you can send a signed notice of revocation;

•

you can grant a new, valid proxy bearing a later date including by telephone or via the internet; or

•

if you are a holder of record, you can attend the URS special meeting and vote in person, which will automatically cancel any proxy previously given, or you may revoke your proxy in person, but your attendance alone will not revoke any proxy that you have previously given.

If you choose either of the first two methods, you must submit your notice of revocation or your new proxy to the Secretary of URS no later than the beginning of the URS special meeting. If you have submitted a proxy for your shares by telephone or via the internet, you may revoke your prior telephone or internet proxy by any manner described above. If your shares are held in street name by your broker, bank or nominee, you should contact your broker, bank or nominee to change your vote.

Q:

How does the AECOM Board of Directors recommend that AECOM stockholders vote?

A:

The AECOM Board of Directors has unanimously determined that the merger agreement and the transactions contemplated by the merger agreement, including the merger and the stock issuance, are advisable and in the best interests of AECOM and its stockholders. The AECOM Board of Directors unanimously recommends that the AECOM stockholders vote (i) "FOR" the stock issuance proposal and (ii) "FOR" the AECOM adjournment proposal.

Q:

How does the URS Board of Directors recommend that URS stockholders vote?

A:

The URS Board of Directors has unanimously determined that the merger agreement and the transactions contemplated by the merger agreement, including the merger, are advisable and in the best interests of URS and its stockholders. The URS Board of Directors unanimously recommends that URS stockholders vote (i) "FOR" the adoption of the merger agreement, (ii) "FOR" the URS adjournment proposal and (iii) "FOR" the golden parachute proposal.

Prior to any decision made by the URS Board of Directors, URS director Lydia Kennard disclosed to the URS Board of Directors that she is President and CEO of KDG Construction Consulting, which is currently a subcontractor to AECOM. Accordingly, she was not present at the meeting in which this transaction was considered by the board and therefore did not participate in any board decision with respect to a transaction with AECOM. Therefore, references in this joint proxy statement/prospectus to the URS Board of Directors are references to all URS directors with the exception of Ms. Kennard, and references to the unanimous approval of the URS Board of Directors are references to unanimous approval, with Ms. Kennard abstaining.

Q:

When do you expect the merger to be completed?

A:

AECOM and URS expect to complete the merger as soon as reasonably practicable and expect the closing of the merger to occur on October 17, 2014, the first business day following the AECOM and URS special stockholder meetings. However, the merger is subject to various regulatory approvals and the satisfaction or waiver of other conditions, and it is possible that factors outside the control of AECOM and URS could result in the merger being completed at a later time or not at all. As a result, there may be a substantial amount of time between the date on which the special meetings are held and the date of the completion of the merger.

Q:

Are stockholders entitled to appraisal rights?

A:

AECOM Stockholders:    No. Under Delaware law, you are not entitled to appraisal rights in connection with the merger.

URS Stockholders:    Depending upon the elections made by holders of shares of URS common stock with respect to the form of consideration to be received in the merger, Delaware law may entitle the holders of shares of URS common stock, who comply with the procedures specified in Section 262 of the Delaware General Corporation Law (the "DGCL"), to have their shares appraised by the Delaware Court of Chancery. Specifically, holders, if any, of shares of URS common stock who make a stock election (as more fully explained below under "The Merger Agreement—Consideration to Be Received in the Merger—Stock Election"), but are forced to accept cash consideration in respect of such shares by reason of proration (and not simply cash in lieu of fractional shares) (as more fully explained below under "The Merger Agreement—Consideration to Be Received in the Merger—Proration"), would be entitled to have the "fair value" of such shares appraised by the Delaware Court of Chancery if they otherwise comply with the procedures of Section 262. Under Delaware law, holders of shares of URS common stock who choose not to make an election with respect to the form of merger consideration to be received for their shares will not be entitled to appraisal rights.

As of the date of the mailing of this joint proxy statement/prospectus, we cannot definitively state whether appraisal rights will be available as a result of the merger because (i) the availability of appraisal rights depends on whether and the extent to which the cash consideration is undersubscribed, and (ii) we will not know whether the cash consideration is undersubscribed to the extent that appraisal rights would be available until the election deadline (as more fully explained below under "The Merger Agreement—Consideration to Be Received in the Merger"). In the event that the cash consideration is undersubscribed to the extent that appraisal rights would be available, URS stockholders who have otherwise complied with the requirements of Section 262 will be advised of the availability of appraisal rights within ten days of the merger in the notice of the effective date of the merger required by Section 262. If the cash consideration is not undersubscribed to the extent that appraisal rights would be available, AECOM will issue a public announcement and file a Current Report on Form 8-K with the SEC informing URS stockholders that appraisal rights will not be available in connection with the merger.

Because URS stockholders may be entitled to appraisal rights under certain circumstances, we urge you to read the summary of appraisal rights contained in this joint proxy statement/prospectus under the section entitled "The Merger—Appraisal Rights," as well as DGCL Section 262, which has been attached hereto as Annex F. If you wish to preserve the ability to exercise appraisal rights, you must make a written demand for appraisal of your shares as described in the section entitled "The Merger—Appraisal Rights" and in DGCL Section 262.

Q:

Who can help answer my questions?

A:

AECOM stockholders or URS stockholders who have questions about the merger or the stock issuance, the other matters to be voted on at the special meetings, or how to submit a proxy, or desire additional copies of this joint proxy statement/prospectus or additional proxy cards should contact:

SUMMARY

        This summary highlights information contained elsewhere in this joint proxy statement/prospectus and may not contain all the information that is important to you with respect to the merger, the stock issuance and the other matters being considered at the AECOM and URS special meetings. AECOM and URS urge you to read the remainder of this joint proxy statement/prospectus carefully, including the attached Annexes, and the other documents to which we have referred you. See also the section entitled "Where You Can Find More Information." We have included page references in this summary to direct you to a more complete description of the topics presented below.

The Companies

AECOM Technology Corporation (See page 40)

        AECOM is a leading provider of professional technical and management support services for public and private clients around the world. AECOM offers its services through two business segments: Professional Technical Services ("PTS") and Management Support Services ("MSS"). AECOM's PTS segment delivers planning, consulting, architectural and engineering design, and program and construction management services to commercial and government clients worldwide in major end markets such as transportation, facilities, environmental, energy, water and government. AECOM's MSS segment provides program and facilities management and maintenance, training, logistics, consulting, technical assistance and systems integration services, primarily for agencies of the U.S. government. AECOM completed the initial public offering of its common stock in May 2007.

        Shares of AECOM common stock are traded on the NYSE under the symbol "ACM." Following the merger, shares of AECOM common stock will continue to be traded on the NYSE under the symbol "ACM."

        The principal executive offices of AECOM are located at 1999 Avenue of the Stars, Suite 2600, Los Angeles, California 90067, and its telephone number is (213) 593-8000.

URS Corporation (See page 40)

        URS provides a broad range of engineering, construction, and technical services to public agencies and private sector companies around the world. URS's Infrastructure & Environment Division provides program management, planning, design, engineering, construction and construction management, operations and maintenance, and decommissioning and closure services to a variety of U.S. and international government agencies and departments, as well as to private sector clients. URS's Federal Services Division provides program management, planning, design engineering, systems engineering and technical assistance, construction and construction management, operations and maintenance, management and operations, IT, and decommissioning and closure services to U.S. federal government agencies, as well as to national governments in other countries. URS's Energy & Construction Division provides program management, planning, design, engineering, construction and construction management, operations and maintenance, and decommissioning and closure services to private sector clients as well as federal, state, and local government agencies. URS's Oil & Gas Division provides oilfield services, such as rig transportation and fluid hauling; oil and gas production services, including mechanical, electrical and instrumentation services; pipeline and facility construction; module fabrication; and maintenance services for oil and gas industry clients throughout the U.S. and Canada.

        URS's common stock is traded on the NYSE under the symbol "URS." Upon completion of the merger, shares of URS common stock currently listed on the NYSE will cease to be listed on the NYSE and will subsequently be deregistered under the Exchange Act.

        The principal executive offices of URS are located at 600 Montgomery Street, 26th Floor, San Francisco, California 94111, and its telephone number is (415) 774-2700.

ACM Mountain I, LLC (See page 40)

        ACM Mountain I, LLC, or Merger Sub, is a wholly owned subsidiary of AECOM and a Delaware limited liability company. Merger Sub was formed on July 3, 2014 for the sole purpose of effecting the merger. In the merger, Merger Sub will be merged with and into URS, with URS surviving as a wholly owned subsidiary of AECOM.

        The principal executive offices of Merger Sub are located at 1999 Avenue of the Stars, Suite 2600, Los Angeles, California 90067, and its telephone number is (213) 593-8000.

ACM Mountain II, LLC (See page 41)

        ACM Mountain II, LLC, or Merger Sub I, is a wholly owned subsidiary of AECOM and a Delaware limited liability company. Merger Sub I was formed on July 3, 2014 for the sole purpose of effecting the second merger. In the second merger, URS will be merged with and into Merger Sub I, with Merger Sub I surviving the second merger as a limited liability company and a wholly owned subsidiary of AECOM.

        The principal executive offices of Merger Sub I are located at 1999 Avenue of the Stars, Suite 2600, Los Angeles, California 90067, and its telephone number is (213) 593-8000.

Risk Factors (See page 31)

        Before voting at the AECOM special meeting or the URS special meeting, you should carefully consider all of the information contained in or incorporated by reference into this joint proxy statement/prospectus, as well as the specific factors under the heading "Risk Factors," including the risks that:

•

Because the market price of AECOM common stock will fluctuate, URS stockholders cannot be sure of the value of the merger consideration they will receive at closing;



•

URS stockholders may receive a form of consideration different from what they elect, depending on the elections of other URS stockholders;



•

The merger is subject to a number of conditions, including certain governmental and regulatory conditions that may not be satisfied, and the merger may not be completed on a timely basis, or at all;



•

If AECOM's debt financing for the merger becomes unavailable, the merger may not be completed;



•

AECOM and URS may be unable to successfully integrate their businesses in order to realize the anticipated benefits of the merger or do so within the intended timeframe; and



•

AECOM expects to incur substantial additional indebtedness to finance the merger, which may decrease AECOM's business flexibility following the merger and adversely affect AECOM's financial results.

The Merger

The Merger Agreement (See page 135)

        AECOM and URS have entered into the merger agreement attached as Annex A to this joint proxy statement/prospectus. AECOM and URS encourage you to read the entire merger agreement carefully because it is the principal document governing the merger and the stock issuance.

Effects of the Merger (See page 58)

        Subject to the terms and conditions of the merger agreement, at the effective time of the merger, Merger Sub will be merged with and into URS, with URS surviving the merger as a wholly owned subsidiary of AECOM. At the effective time of the second merger, which will be immediately following the merger, and as part of a single integrated transaction with the merger, URS will be merged with and into Merger Sub I, with Merger Sub I surviving the second merger as a limited liability company and a wholly owned subsidiary of AECOM. There are no conditions to the second merger other than consummation of the merger. We expect that, on a fully diluted basis, following the merger, the existing stockholders of AECOM (together with holders of AECOM equity-based awards) will collectively own approximately 66% of the outstanding AECOM common stock, while the current stockholders of URS, together with the holders of URS election award shares and URS roll-over award shares, will collectively own approximately 34% of the outstanding AECOM common stock.

Consideration to Be Received in the Merger (See page 136)

        If the merger is completed, URS stockholders will have the right to elect to receive merger consideration for each of their shares of URS common stock in the form of cash or shares of AECOM common stock, subject to proration in the circumstances described below. In the event of proration, a URS stockholder may receive a portion of the merger consideration in a form other than that which such stockholder elected. If the aggregate consideration to be paid to any holder of URS common stock would result in such holder receiving a fractional share of AECOM common stock, cash will be paid in lieu of such fractional share.

        The value of the merger consideration will fluctuate with the market price of the AECOM common stock and will be determined based on the average five-day AECOM closing price. As explained in more detail in this joint proxy statement/prospectus, whether a URS stockholder makes a cash election, a stock election or no election, the value of the consideration that such stockholder receives as of the date of completion of the merger will be approximately equivalent based on the average five-day AECOM closing price used to calculate the merger consideration. A URS stockholder may specify different elections with respect to different shares that such stockholder holds (e.g., if a URS stockholder owns 100 shares of URS common stock, that stockholder could make a cash election with respect to 50 shares and a stock election with respect to the other 50 shares).

        The aggregate amount of cash to be paid to holders of URS common stock (not including, for this purpose, URS election award shares) as of immediately prior to closing is fixed in the merger agreement at $2,257,950,321. As a result, if the cash election is oversubscribed or undersubscribed, then certain adjustments will be made to the merger consideration to proportionately reduce the cash or stock amounts received by the URS stockholders in the manner described below in the section entitled "The Merger Agreement—Consideration to Be Received in the Merger—Proration." To the extent that the number of outstanding shares of URS increases between the date of the merger agreement and the effective time of the merger, due to the vesting of stock-settled awards or as otherwise permitted by the merger agreement, the aggregate number of shares of AECOM common stock to be issued as consideration in the merger will be increased accordingly, but the aggregate amount of cash to be paid as consideration will not change.

        As an example, based on the average (rounded to the nearest one tenth of a cent) of the closing prices of AECOM common stock for the five trading days ending on July 11, 2014 (the last trading day before announcement of the merger), for each share of URS common stock held, a URS stockholder would receive either approximately $56.41 in cash or 1.7687 shares of AECOM common stock, having a market value of $31.89 based on such average AECOM closing price, subject to proration if cash was oversubscribed or undersubscribed. As another example, based on the average (rounded to the nearest one tenth of a cent) of the closing prices of AECOM common stock for the five trading days ending on

September 12, 2014 (the most recent practicable trading date before filing of this joint proxy statement/prospectus), for each share of URS common stock held, a URS stockholder would receive either approximately $60.44 in cash or 1.6166 shares of AECOM common stock, having a market value of $37.388 based on such average AECOM closing price, subject to proration if cash was oversubscribed or undersubscribed. We will compute the actual amount of cash and number of shares of AECOM common stock that each URS stockholder will receive in the merger using the formula contained in the merger agreement. For a summary of the formula contained in the merger agreement, see "The Merger Agreement—Consideration to be Received in the Merger."

        The following table illustrates the value of the merger consideration for different hypothetical five-day average closing prices of the AECOM common stock on the NYSE for the five trading days immediately preceding the day on which the merger is completed and, for illustrative purposes only, the effects of proration assuming that 70% of URS shares elect cash consideration and 30% of URS shares elect stock consideration. For simplicity, the table assumes that there are 68,545,117 shares of URS common stock outstanding (which represents the number of shares of URS common stock outstanding on September 12, 2014, the most recent practicable day before filing of this joint proxy statement/prospectus), that all URS stockholders make elections and that no URS stockholders have exercised appraisal rights.

        The table above is illustrative only. The value of the merger consideration that a URS stockholder actually receives will be based on the actual average five-day AECOM closing price, as described below. The actual average five-day AECOM closing price may be outside the range of the amounts set forth above and, as a result, the actual value of the merger consideration per share of URS common stock may not be shown in the above table.

Election Form (See page 141)

        Record holders of shares of URS common stock (other than holders of URS restricted stock) on September 12, 2014, the URS record date, are receiving an election form enclosed with this joint proxy statement/prospectus with instructions for making cash and/or stock elections. URS stockholders must properly complete and deliver to the exchange agent an election form by 2:00 p.m., California time, on October 15, 2014, the election deadline, accompanied by their URS stock certificates (or a properly completed notice of guaranteed delivery). The election form also includes delivery instructions with respect to book-entry shares. URS stockholders should NOT send in their stock certificates with their proxy card. Once URS stockholders have tendered their URS stock certificates to the exchange agent, they may not transfer their shares of URS common stock represented by those stock certificates until the merger is completed, unless they revoke their election by written notice to the exchange agent, or withdraw the certificates representing their shares, prior to the election deadline. If the merger is not completed and the merger agreement is terminated, stock certificates will be returned by the exchange agent.

        If URS stockholders fail to submit a properly completed election form, together with their URS stock certificates (or a properly completed notice of guaranteed delivery), if any, prior to the election deadline, they will be deemed not to have made an election. As non-electing holders, they will be paid merger consideration in an amount per share that is approximately equivalent in value to the amount paid per share to holders making elections, but they may be paid in all cash, in all AECOM common stock, or in part cash and in part AECOM common stock, depending on the remaining pool of cash and AECOM common stock available for paying merger consideration after honoring the cash elections and stock elections that other stockholders have made, subject to proration, and without regard to the preferences of such non-electing holders.

Treatment of URS Restricted Stock, Restricted Stock Units and Other Equity-Based Incentive Awards (See page 143)

        If the merger is completed, URS roll-over award shares will be assumed by AECOM and converted into AECOM equity awards as follows:

•

Certain URS Time Vesting Restricted Stock Units and Restricted Stock Awards.  Upon consummation of the merger, each outstanding and unvested URS restricted stock unit and URS restricted stock award that vests solely based on the passage of time and that does not vest by its terms upon the consummation of the merger will be assumed by AECOM and converted into restricted stock and restricted stock units with respect to whole shares of AECOM common stock, on the same terms and conditions as applied to such URS restricted stock unit and URS restricted stock awards immediately prior to the consummation of the merger, with the number of shares of AECOM common stock subject to each such assumed share of restricted stock and restricted stock unit determined based upon the exchange ratio, which is the quotient, rounded to the nearest one ten thousandth, obtained by dividing the per share cash amount (which is the amount obtained by adding (i) $33.00 and (ii) the product of 0.734 times the average five-day AECOM closing price) by the average five-day AECOM closing price. Any corresponding accrued but unpaid dividends and dividend equivalents with respect to such URS restricted stock units and URS restricted stock awards will also be assumed by AECOM and remain outstanding as an obligation with respect to the converted award.

        In addition, if the merger is completed, holders of URS election award shares will have the right to elect to receive merger consideration in the form of cash or shares of AECOM common stock, subject to proration in the circumstances described in the enclosed joint proxy statement/prospectus:

•

Certain URS Time Vesting Restricted Stock Units and Restricted Stock Awards.  Immediately prior to the consummation of the merger, each outstanding URS restricted stock unit and URS

restricted stock award that vests solely based on the passage of time and that either is vested, but not yet settled at the time the merger is consummated or that vests by its terms upon the consummation of the merger will immediately and automatically vest and entitle the holder thereof to the merger consideration, subject to proration, and the holder will be entitled to any corresponding accrued but unpaid dividends or dividend equivalents (less applicable withholding), which will be paid and/or delivered, as applicable, within thirty (30) days after the closing date, subject to certain limited exceptions.

•

Performance Vesting Restricted Stock Units and Restricted Stock Awards.  Immediately prior to the consummation of the merger, each outstanding URS restricted stock unit and URS restricted stock award that vests, in whole or in part, based on the achievement of performance goals (other than the performance-based awards granted in March 2013 with a two-year performance period ending January 2, 2015, which will only vest if the applicable performance goal is determined to be achieved measured as of the month-end prior to the effective time), will immediately and automatically vest based on the deemed achievement of the performance goals at target level and entitle the holder thereof to the merger consideration, subject to proration, and the holder will be entitled to any corresponding accrued but unpaid dividends or dividend equivalents (less applicable withholding), which will be paid and/or delivered, as applicable, within forty-five (45) days after the closing date, subject to certain limited exceptions.



•

Deferred Stock Units and Deferred Restricted Stock Units.  Upon consummation of the merger, each outstanding URS deferred stock award held by a non-employee director and each outstanding URS deferred restricted stock unit, all of which are vested, will entitle the holder thereof to the merger consideration, subject to proration. The delivery and/or payment, as applicable, of the merger consideration and any dividend equivalents will be made on the first business day that follows the six (6) month anniversary of the holder's separation from service with URS and AECOM, subject to certain limited exceptions.

Financing (See page 121)

        In connection with the merger agreement, on July 11, 2014, AECOM entered into a commitment letter with Bank of America, N.A. and Merrill Lynch, Pierce, Fenner & Smith Incorporated, which was amended by the parties on July 24, 2014. On August 2, 2014, AECOM entered into an amended and restated commitment letter (the "A&R commitment letter"), with Bank of America, N.A., Merrill Lynch, Pierce, Fenner & Smith Incorporated, MUFG Union Bank, N.A., The Bank of Nova Scotia, BNP Paribas, BNP Paribas Securities Corp., JPMorgan Chase Bank, N.A., J.P. Morgan Securities LLC, BBVA Compass, Wells Fargo Bank, National Association, Sumitomo Mitsui Banking Corporation, Crédit Agricole Corporate and Investment Bank, Morgan Stanley Senior Funding, Inc., HSBC Bank USA, National Association and HSBC Securities (USA) Inc. (the "debt financing sources"), pursuant to which the debt financing sources have committed, subject to customary conditions, to provide AECOM with $6.3 billion of debt financing in support of the transactions contemplated by the merger agreement. Prior to closing the merger, AECOM anticipates syndicating the committed debt financings which may modify the size of certain tranches of debt relative to those specified in the A&R commitment letter. The debt financing is currently anticipated to consist of a term loan A facility in an aggregate principal amount of $1.85 billion, a revolving credit facility in an aggregate principal amount of $1.05 billion, a $1.263 billion term loan B, and an incremental performance letter of credit facility in an aggregate amount of $500 million available solely for the issuance of performance letters of credit. In addition, AECOM anticipates that $1.6 billion of the $3.4 billion "term loan B" facility originally contemplated under the A&R commitment letter will be replaced by issuance of $800 million in 8-year senior unsecured notes, and $800 million in 10-year senior unsecured notes. The completion of the merger is not subject to a financing condition.

Recommendation of the Board of Directors of AECOM (See page 76)

        In evaluating the merger, the AECOM Board of Directors consulted with AECOM's management and legal and financial advisors, and in reaching its decision to approve the merger agreement and recommend approval by AECOM stockholders of the stock issuance, the AECOM Board of Directors also considered a number of factors that the AECOM Board of Directors views as supporting its decision, including, but not limited to, the following:

•

the combination of AECOM and URS is expected to create an industry leader with the ability to deliver more capabilities from a broad global platform to reach more clients in more industry end markets;



•

the merger is expected to create a company with a greater size and economies of scale, which should enable it to have the ability to respond to competitive pressures and an increased opportunity to compete profitably;



•

the merger accelerates AECOM's strategy of offering an integrated-delivery model by adding key capabilities and expertise in markets such as construction, oil & gas, power and government services;



•

the transaction is expected to be accretive to AECOM's earnings per share and more than 25% accretive to its cash earnings per share in fiscal year 2015, excluding transaction-related costs; and



•

annual cost synergies of $250 million are expected, nearly all of which AECOM expects to achieve by the end of fiscal year 2016.

        After careful consideration, the AECOM Board of Directors unanimously approved the merger agreement and the transactions contemplated thereby, including the mergers and the stock issuance, and determined that the merger agreement and the transactions contemplated thereby, including the merger and the stock issuance, are advisable and in the best interests of AECOM and its stockholders. For more information regarding the factors considered by the AECOM Board of Directors in reaching its decision to approve the merger agreement and the transactions thereby contemplated, see the section entitled "The Merger—AECOM's Reasons for the Merger; Recommendation of the AECOM Board of Directors."

        The AECOM Board of Directors unanimously recommends that the AECOM stockholders vote (i) "FOR" the stock issuance proposal and (ii) "FOR" the AECOM adjournment proposal.

Recommendation of the Board of Directors of URS (See page 96)

        In reaching its decision to approve the merger agreement and recommend adoption of the merger agreement by the URS stockholders, the URS Board of Directors consulted with URS's management, as well as with URS's legal and financial advisors, and also considered a number of factors that the URS Board of Directors views as supporting its decision, including, but not limited to, the following:

•

their perspectives on URS's projections and views on macroeconomic and industry trends, and their views that a transaction with AECOM could enhance URS's ability to compete with other globally expanding firms and pursue large projects;



•

their knowledge of URS's business, financial condition, results of operations, industry, competitors and prospects as a standalone company;



•

the financial terms of the merger, including the fact that, based on the closing price on the NYSE of AECOM common stock on July 10, 2014 (the last trading day prior to the execution of the merger agreement), the merger consideration represented an approximate 20% premium over the trailing 30-day average closing price of URS common stock on the NYSE ending on July 10, 2014;

•

their knowledge of AECOM's business, financial condition, results of operations, industry, competitors and prospects, taking into account the results of the URS Board of Directors' and the Value Creation Committee' due diligence review of AECOM; and



•

the review of strategic alternatives conducted by the URS Board of Directors and the Value Creation Committee of the URS Board of Directors (the "Value Creation Committee") and their financial advisors and the belief of the URS Board of Directors, following such review, that the merger would provide greater value to URS stockholders than other potential strategic alternatives available to URS.

        After careful consideration, the URS Board of Directors unanimously approved and adopted the merger agreement and determined that the merger agreement and the transactions contemplated thereby, including the merger, are advisable and in the best interests of URS and its stockholders. For more information regarding the factors considered by the URS Board of Directors in reaching its decision to approve the merger agreement and the merger, see the section entitled "The Merger—URS's Reasons for the Merger; Recommendation of the URS Board of Directors."

        The URS Board of Directors unanimously recommends that URS stockholders vote (i) "FOR" the adoption of the merger agreement, (ii) "FOR" the URS adjournment proposal and (iii) "FOR" the golden parachute proposal.

Opinion of AECOM's Financial Advisor—BofA Merrill Lynch (See page 78)

        In connection with the merger, Merrill Lynch, Pierce, Fenner & Smith Incorporated (which we refer to as "BofA Merrill Lynch"), a financial advisor to AECOM, delivered a written opinion, dated July 11, 2014, to the AECOM Board of Directors as to the fairness, from a financial point of view and as of the date of the opinion, to AECOM of the consideration to be paid by AECOM in the merger. The full text of BofA Merrill Lynch's written opinion is attached as Annex B to this joint proxy statement/prospectus and sets forth, among other things, the assumptions made, procedures followed, factors considered and limitations on the review undertaken by BofA Merrill Lynch in rendering its opinion. BofA Merrill Lynch delivered its opinion to the AECOM Board of Directors for the benefit and use of the AECOM Board of Directors (in its capacity as such) in connection with and for purposes of its evaluation of the merger consideration from a financial point of view to AECOM. BofA Merrill Lynch's opinion did not address any other aspect of the mergers and no opinion or view was expressed as to the relative merits of the mergers in comparison to other strategies or transactions that might be available to AECOM or in which AECOM might engage or as to the underlying business decision of AECOM to proceed with or effect the mergers. BofA Merrill Lynch expressed no opinion or recommendation as to how any stockholder should vote or act in connection with the mergers or any other matter.

Opinion of AECOM's Financial Advisor—Moelis & Company LLC (See page 87)

        In connection with the merger, AECOM's Board of Directors received a written opinion, dated July 11, 2014, from Moelis & Company LLC, referred to as Moelis, as to the fairness, from a financial point of view and as of the date of such opinion, to AECOM of the consideration to be paid by AECOM in the merger. The full text of Moelis' written opinion dated July 11, 2014, which sets forth the assumptions made, procedures followed, matters considered and limitations on the review undertaken in connection with the opinion, is attached as Annex C to this joint proxy statement/prospectus and is incorporated herein by reference. Stockholders are urged to read Moelis' written opinion carefully and in its entirety. Moelis' opinion was provided for the use and benefit of AECOM's Board of Directors (in its capacity as such) in its evaluation of the merger. Moelis' opinion is limited solely to the fairness, from a financial point of view and as of the date of such opinion, to AECOM of the consideration to be paid by AECOM in the merger and does not address AECOM's underlying business decision to effect the merger or the relative merits of the merger as compared to any

alternative business strategies or transactions that might be available with respect to AECOM. Moelis' opinion does not constitute a recommendation to any stockholder of AECOM as to how such stockholder should vote or act with respect to the merger or any other matter.

Opinion of URS's Financial Advisor—Citigroup Global Markets Inc. (See page 101)

        In connection with the merger, the URS Board of Directors received an opinion, dated July 11, 2014, from Citigroup Global Markets Inc. ("Citigroup"), as to the fairness, from a financial point of view, of the cash consideration and the stock consideration, taken in the aggregate, to be received pursuant to the terms and subject to the conditions set forth in the merger agreement by holders of URS common stock (other than shares of URS common stock held in treasury by URS, or owned, directly or indirectly, by AECOM or Merger Sub or as to which dissenters' rights have been perfected).

        The full text of Citigroup's written opinion, which sets forth, among other things, the procedures followed, assumptions made, matters considered and limitations on the scope of review undertaken in rendering its opinion is attached as Annex D to this joint proxy statement/prospectus. The opinion of Citigroup was provided for the information of the URS Board of Directors in connection with its evaluation of the proposed merger. The opinion is not intended to be and does not constitute a recommendation to any stockholder as to how such stockholder should vote or act on, or make an election with respect to, any matters relating to the proposed merger. See also "The Merger—Opinion of URS's Financial Advisor—Citigroup Global Markets Inc."

Opinion of URS's Financial Advisor—Dean Bradley Osborne Partners LLC (See page 109)

        Dean Bradley Osborne Partners LLC ("DBO Partners") delivered its opinion to URS's Board of Directors that, as of July 11, 2014, and based upon and subject to the factors and assumptions set forth therein, the merger consideration to be received by the holders of shares of URS common stock pursuant to the merger agreement was fair from a financial point of view to the holders of shares of URS common stock.

        The full text of the written opinion of DBO Partners, dated July 11, 2014, which sets forth assumptions made, procedures followed, matters considered and limitations on the review undertaken in connection with the opinion, is attached as Annex E to this joint proxy statement/prospectus. The opinion of DBO Partners was provided for the information and assistance of URS's Board of Directors and addresses only the fairness from a financial point of view of the consideration to be received by the holders of shares of URS common stock pursuant to the merger agreement. The DBO Partners opinion is not a recommendation as to how stockholders of URS or AECOM should vote at the stockholders' meetings or as to how stockholders of URS should make any election with respect to the mergers.

Interests of AECOM's Directors and Executive Officers in the Merger (See page 122)

        Other than continuing roles as executive officers of AECOM after the effective time of the merger, the members of the AECOM executive management team do not have any interests in the merger that are different from, or in addition to, the interests of AECOM stockholders generally. In addition, other than continuing membership on the Board of Directors of AECOM after the effective time of the merger, the members of the AECOM Board of Directors do not have any interests in the merger that are different from, or in addition to, the interests of AECOM stockholders generally. The AECOM Board of Directors was aware of these interests and considered them, among other matters, in approving the merger agreement and the transactions contemplated by the merger agreement, including the merger and the stock issuance, and in recommending that AECOM stockholders vote to approve the stock issuance and AECOM adjournment. For additional information regarding the interests of AECOM directors and executive officers in the merger, please see the section entitled "The Merger—Interests of AECOM's Directors and Executive Officers in the Merger."

Interests of URS's Directors and Executive Officers in the Merger (See page 122)

        Executive officers and members of the URS Board of Directors have interests in the merger that may be in addition to, or different from, the interests of URS stockholders generally. URS's Board of Directors was aware of these interests and considered them, among other matters, in approving the merger and the merger agreement and in making the recommendations that the URS stockholders approve and adopt the merger agreement and approve the merger and the other transactions contemplated by the merger agreement.

        As detailed below under "The Merger—Interests of URS's Directors and Executive Officers in the Merger," upon and following the merger, certain of URS's executive officers may become entitled to, among other things, (i) acceleration of vesting of certain equity-based awards, (ii) enhanced severance payments and/or benefits and, for one executive officer who is not a named executive officer, reimbursement of excise taxes and/or (iii) continuation of certain indemnification insurance.

        As detailed below under "The Merger—AECOM Board of Directors and Management Following the Merger," certain of URS's executive officers and members of the URS Board of Directors will continue to serve as officers or directors of the combined company or URS (as a subsidiary of AECOM) upon completion of the merger. Effective upon the completion of the merger, AECOM will expand the size of its Board of Directors from 11 to 13 directors and will elect two persons who were members of the URS Board of Directors immediately prior to the effective time of the merger to the AECOM Board of Directors. The election of these directors will be subject to the approval and related processes of AECOM's Nominating, Governance and Risk Committee. On July 3, 2014, Michael S. Burke, President and Chief Executive Officer of AECOM, sent Martin Koffel, Chief Executive Officer of URS, a signed letter to confirm AECOM's intentions for leadership appointments at the combined company, which included roles for certain of URS's executive officers, including in the combined company's integration activities. On September 2, 2014, AECOM and URS announced that URS executive officers, Tom Bishop, George Nash, Randy Wotring, and Wayne Shaw would each have prominent roles in the combined company with Mr. Bishop to lead the Design and Consulting Services Group in the Americas, Mr. Nash to be Group President of Energy, Infrastructure, and Industrial Construction, Mr. Wotring to be Group President of Management Services and Mr. Shaw to serve as President of the combined company's Canadian-based Oil & Gas business.

Governance Matters Following the Merger (See page 155)

        Effective upon completion of the merger, AECOM will expand the size of its Board of Directors from 11 to 13 directors and will elect two persons who were members of the URS Board of Directors immediately prior to the effective time of the merger to the AECOM Board of Directors. The parties have agreed that by August 25, 2014, URS's Chairman and CEO and Lead Independent Director will meet with AECOM's CEO, Chairman of the Nominating, Governance and Risk Committee and Lead Independent Director to develop mutually agreed qualifications for the two URS directors to be elected to the AECOM Board of Directors. The election of these directors will be subject to the approval and related processes of AECOM's Nominating, Governance and Risk Committee.

        Effective as of the effective time of the merger, all of the existing directors of URS will resign. In the event that the merger is not completed, the foregoing director elections and director resignations will not take effect.

        In addition, as described in "The Merger—Interests of URS's Directors and Executive Officers in the Merger—Positions with AECOM Following the Merger", certain of URS's executive officers are expected to continue to serve as officers of AECOM or URS (as a subsidiary of AECOM) upon completion of the merger.

Antitrust Clearances Required for the Merger (See page 129)

        AECOM and URS have each agreed to take certain actions in order to obtain regulatory clearance required to consummate the merger. Regulatory approvals required to complete the merger includes expiration or termination of the required waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, and the rules and regulations promulgated thereunder (the "HSR Act"), following required notifications and review by the Antitrust Division of the U.S. Department of Justice (the "Antitrust Division") or the Federal Trade Commission (the "FTC") and antitrust clearance for the merger under the Competition Act (Canada). The parties filed the required notifications with the Antitrust Division and the FTC on July 22, 2014 and received notice of early termination on August 4, 2014. AECOM and URS also filed notices with antitrust and competition authorities in Canada on August 8, 2014 and on August 21, 2014, the Canadian Competition Bureau issued a no action letter indicating the Commissioner of Competition does not at this time intend to the challenge the proposed transaction before the Canadian Competition Tribunal. While the merger agreement also provides that approval under the antitrust and competition laws of Ireland is a required condition to the merger, the parties have jointly determined that a filing in Ireland is not required and have waived such approval as a condition to closing of the merger. The parties also filed a notice with the antitrust and competition authority in the United Kingdom on August 15, 2014.

        While AECOM and URS expect to obtain all required regulatory clearances, we cannot assure you that these regulatory clearances will be obtained or that the granting of these regulatory clearances will not involve the imposition of additional conditions on the completion of the merger, including the requirement to divest assets, or require changes to the terms of the merger agreement. These conditions or changes could result in the conditions to the merger not being satisfied.

Effective Time and Completion of the Merger (See page 136)

        AECOM and URS expect to complete the merger as soon as reasonably practicable and expect the closing of the merger to occur on October 17, 2014, the first business day following the AECOM and URS special stockholder meetings. However, the merger is subject to various regulatory approvals and the satisfaction or waiver of other conditions, and it is possible that factors outside the control of AECOM and URS could result in the merger being completed at a later time or not at all. As a result, there may be a substantial amount of time between the dates on which the special meetings are held and the date on which the merger is completed.

Conditions to Completion of the Merger (See page 157)

        The obligations of AECOM and URS to complete the merger are subject to the satisfaction of the following conditions:

•

approval by the AECOM stockholders of the stock issuance proposal;



•

adoption by the URS stockholders of the merger agreement;



•

authorization of the listing on the NYSE of the AECOM shares of common stock to be issued in the merger, subject to official notice of issuance;



•

the waiting period (and any extension thereof) applicable to the merger under the HSR Act having expired or been earlier terminated (which condition was satisfied on August 4, 2014 when the FTC granted early termination of the HSR waiting period);



•

receiving antitrust clearance for the merger under the Competition Act (Canada) (which condition was satisfied on August 21, 2014 when the Canadian Competition Bureau issued a no action letter) and the Ireland Competition Act (which Ireland clearance was waived by the parties);

•

effectiveness of the registration statement of which this joint proxy statement/prospectus forms a part and the absence of a stop order or proceedings threatened or initiated by the SEC for that purpose; and



•

no temporary restraining order, preliminary or permanent injunction or other judgment, order or decree issued by any court of competent jurisdiction or other legal restraint or prohibition will be in effect, and no law will have been enacted, entered, promulgated, enforced or deemed applicable by any governmental entity that, in any such case, prohibits or makes illegal the consummation of the merger.

        In addition, AECOM's, Merger Sub's and Merger Sub I's obligations to effect the merger is subject to the satisfaction or waiver of the following additional conditions:

•

certain of the representations and warranties of URS, including those regarding corporate organization, corporate authorization, the absence of any material adverse effect, SEC reports, information included in this joint proxy statement/prospectus, the absence of a shareholders rights' plan and the absence of any applicable state takeover statutes, must be true and correct as of July 11, 2014, and as of the closing date of the merger, as if made on the closing date (except to the extent such representations and warranties expressly relate to an earlier date, in which case as of such earlier date);



•

certain of the representations and warranties of URS related to capital stock must be true and correct (except for de minimis inaccuracies) as of July 11, 2014 and as of the closing date of the merger as if made as on the closing date of the merger (except to the extent such representations and warranties expressly relate to an earlier date, in which case as of such earlier date);



•

certain of the representations and warranties of URS related to the vesting of its equity awards must be true and correct in all material respects as of July 11, 2014, and as of the closing date of the merger as if made on the closing date;



•

each of the other representations and warranties of URS that are qualified as to materiality or material adverse effect (disregarding all materiality and material adverse effect qualifications contained therein) must be true and correct as of July 11, 2014, and as of the closing date of the merger as if made on the closing date (except to the extent such representations and warranties expressly relate to an earlier date, in which case as of such earlier date);



•

URS having performed or complied with, in all material respects, all of its obligations under the merger agreement at or prior to the effective time of the merger;



•

receipt of a certificate executed by an executive officer of URS as to the satisfaction of the conditions described in the preceding five bullet points;



•

the receipt of all consents or approvals of any governmental entity required to be obtained in connection with the merger (other than any consents or approvals under applicable antitrust or competition laws), which approvals will have been granted without any limitation, restriction or condition that, individually or in the aggregate, has had or would reasonably be expected to have a material adverse effect;



•

the absence, since July 11, 2014, of any event, change, circumstance, occurrence, effect or state of facts that, individually or in the aggregate, has had, or would reasonably be expected to have, a material adverse effect on URS; and



•

AECOM having received from its counsel a written opinion to the effect that the mergers, taken together, will qualify as a "reorganization" within the meaning of Section 368(a) of the Code.

        In addition, URS's obligations to effect the merger is subject to the satisfaction or waiver of the following additional conditions:

•

certain of the representations and warranties of AECOM, Merger Sub and Merger Sub I, including those regarding corporate organization, corporate authorization, the absence of any material adverse effect, SEC reports, and information included in this joint proxy statement/prospectus, must be true and correct as of July 11, 2014, and as of the closing date of the merger, as if made on the closing date (except to the extent such representations and warranties expressly relate to an earlier date, in which case as of such earlier date);



•

certain of the representations and warranties of AECOM, Merger Sub and Merger Sub I related to capital stock must be true and correct (except for de minimis inaccuracies) as of July 11, 2014 and as of the closing date of the merger as if made as on the closing date of the merger (except to the extent such representations and warranties expressly relate to an earlier date, in which case as of such earlier date);



•

each of the other representations and warranties of AECOM, Merger Sub and Merger Sub I that are qualified as to materiality or material adverse effect (disregarding all materiality and material adverse effect qualifications contained therein) must be true and correct as of July 11, 2014, and as of the closing date of the merger as if made on the closing date (except to the extent such representations and warranties expressly relate to an earlier date, in which case as of such earlier date);



•

AECOM, Merger Sub and Merger Sub I having performed or complied with, in all material respects, all of their obligations under the merger agreement at or prior to the effective time of the merger;



•

receipt of a certificate executed by an executive officer of AECOM as to the satisfaction of the conditions described in the preceding four bullet points; and



•

URS having received from its counsel a written opinion to the effect that the mergers, taken together, will qualify as a "reorganization" within the meaning of Section 368(a) of the Code.

        There are no conditions to the second merger other than consummation of the merger.

No Solicitation of Alternative Proposals (See page 150)

        The merger agreement precludes AECOM and URS from soliciting or engaging in discussions or negotiations with a third party with respect to a proposal for a competing transaction, including the acquisition of a significant interest in AECOM's or URS's common stock or assets. However, if AECOM or URS receives an unsolicited written proposal from a third party (which proposal was not received in violation of such party's non-solicitation obligations) for a competing transaction that AECOM's or URS's Board of Directors, as applicable, among other things, (i) determines in good faith (after consultation with its outside counsel and financial advisors) constitutes or is reasonably likely to lead to a proposal that is superior to the merger and (ii) determines in good faith (after consultation with outside counsel) with respect to which the failure to enter into discussions would result in a breach of its fiduciary duties under applicable law, AECOM or URS, as applicable, may, subject to certain conditions, including after providing four business days' advance notice to the other, furnish non-public information to and enter into discussions with, and only with, that third party regarding such competing transaction.

        See the section entitled "The Merger Agreement—No Solicitation of Alternative Proposals" for a further discussion of each party's covenant not to solicit alternative acquisition proposals.

Termination of the Merger Agreement (See page 159)

        Generally, the merger agreement may be terminated and the merger may be abandoned at any time prior to the completion of the merger (except as specified below, including after the required AECOM stockholder approval or URS stockholder approval are obtained):

•

by mutual written consent of AECOM and URS;



•

by either AECOM or URS:



•

if the merger is not consummated on or before April 11, 2015, subject to extension by either AECOM or URS to July 11, 2015, if all of the conditions to closing have been satisfied as of April 11, 2015, other than conditions related to the HSR Act (which condition was satisfied on August 4, 2014), Competition Act (Canada) (which condition was satisfied on August 21, 2014) and the Ireland Competition Act (which condition the parties have waived) (such date, as it may be extended, the "end date"); except that no party may so terminate the merger agreement if such party's failure to fulfill in any material respect any of its obligations under the merger agreement was the primary cause of the failure of the merger to be consummated by the end date;



•

if any court of competent jurisdiction or other governmental entity issues a final and nonappealable order enjoining or otherwise prohibiting the completion of the merger; except that neither AECOM nor URS may so terminate the merger agreement if it shall not have used its reasonable best efforts to contest, appeal and remove such order;



•

if the AECOM stockholders fail to approve the stock issuance at the AECOM special meeting (or any adjournment or postponement thereof);



•

if the URS stockholders fail to adopt the merger agreement at the URS special meeting (or any adjournment or postponement thereof);



•

if the other party shall have breached any covenant or agreement, or if any representation or warranty of the other party shall become untrue, in either case such that the conditions to the other party's obligations to complete the merger would not then be satisfied and such failure is not reasonably capable of being cured by the earlier of the end date or 30 days after the written notice of such failure; except that neither AECOM nor URS may so terminate the merger agreement if such party is then in material breach of its covenants or agreements under the merger agreement;



•

if the other party changes or withdraws its recommendation in favor of the merger agreement (in the case of URS) or the stock issuance proposal (in the case of AECOM);



•

if the other party shall have failed, upon a request to do so, to publicly reaffirm its recommendation of the merger agreement (if the other party is URS) or the stock issuance proposal (if the other party is AECOM) within ten business days after any competing acquisition proposal or material modification thereto is first announced, distributed or disseminated to the other party's stockholders;



•

if the other party shall have materially breached or failed to perform certain of its obligations related to non-solicitation or the requirement to hold a special meeting of its stockholders to approve the merger agreement (if the other party is URS) or the stock issuance proposal (if the other party is AECOM); or



•

prior to obtaining stockholder approval in favor of the merger agreement (in the case of URS) or the stock issuance proposal (in the case of AECOM), in order to enter into an agreement with respect to a superior proposal; or



•

by URS, if AECOM fails to consummate the merger by a permitted closing date because of failure to receive the proceeds from AECOM's debt financing, as long as the conditions to the

merger would have been satisfied if the closing were held at the time of the termination, and URS stands ready, willing and able to consummate the merger at the time of termination.

        See the section entitled "The Merger Agreement—Termination of the Merger Agreement" for a further discussion of the rights of each of AECOM and URS to terminate the merger agreement.

Expenses and Termination Fees; Liability for Breach (See page 160)

        Each party will generally pay all fees and expenses incurred by it in connection with the merger and the other transactions contemplated by the merger agreement, except that AECOM and URS will share equally all fees and expenses in relation to the printing, filing and mailing of this joint proxy statement/prospectus and any filing or other fees paid to the SEC, in each case in connection with the merger (other than attorneys' fees, accountants' fees and related expenses). AECOM will generally reimburse URS for expenses incurred in cooperating with AECOM's debt financing.

        In certain circumstances in connection with the termination of the merger agreement, AECOM must pay to URS a termination fee equal to $140 million, or $240 million if the merger agreement is terminated by URS under circumstances where all closing conditions have been satisfied but AECOM's debt financing is not available to complete the merger and AECOM fails to close the merger. In certain circumstances in connection with the termination of the merger agreement, URS must pay to AECOM a termination fee equal to $140 million. If the merger agreement is terminated by a party as a result of certain breaches by the other party, then the non-terminating party will be required to reimburse the terminating party for its reasonable out-of-pocket fees and expenses up to $40 million.

        See the section entitled "The Merger Agreement—Expenses and Termination Fees; Liability for Breach" for a further discussion of the circumstances under which such termination fees and/or expense reimbursement will be required to be paid.

Accounting Treatment (See page 166)

        Each of AECOM and URS prepares its financial statements in accordance with GAAP. The merger will be accounted for using the acquisition method of accounting with AECOM treated as the acquiror of URS for accounting purposes.

        See the section entitled "Accounting Treatment" for a further discussion of the accounting treatment of the transaction.

Appraisal Rights (See page 130)

        Depending upon the elections made by holders of shares of URS common stock with respect to the form of consideration to be received in the merger, Delaware law may entitle the holders of shares of URS common stock, who comply with the procedures specified in Section 262 of the DGCL, to have their shares appraised by the Delaware Court of Chancery. Specifically, holders, if any, of shares of URS common stock who make a stock election (as more fully explained below under "The Merger Agreement—Consideration to Be Received in the Merger—Stock Election"), but are forced to accept cash consideration in respect of such shares by reason of proration (and not simply cash in lieu of fractional shares) (as more fully explained below under "The Merger Agreement—Consideration to Be Received in the Merger—Proration"), would be entitled to have the "fair value" of such shares appraised by the Delaware Court of Chancery if they otherwise comply with the procedures set forth in Section 262. Under Delaware law, holders of shares of URS common stock who choose not to make an election with respect to the form of merger consideration to be received for their shares will not be entitled to appraisal rights.

        As of the date of the mailing of this joint proxy statement/prospectus, we cannot definitively state whether appraisal rights will be available as a result of the merger because (i) the availability of appraisal rights depends on whether the cash consideration is undersubscribed to the extent that appraisal rights would be available, and (ii) we will not know whether the cash consideration is

undersubscribed to the extent that appraisal rights would be available until the election deadline (as more fully explained below under "The Merger Agreement—Consideration to Be Received in the Merger"). In the event that the cash consideration is undersubscribed to the extent that appraisal rights would be available, URS stockholders who have otherwise complied with the requirements of Section 262 will be advised of the availability of appraisal rights within ten days of the merger in the notice of the effective date of the merger required by Section 262. If the cash consideration is not undersubscribed to the extent that appraisal rights would be available, AECOM will issue a public announcement and file a Current Report on Form 8-K with the SEC informing URS stockholders that appraisal rights will not be available in connection with the merger.

        Because URS stockholders may be entitled to appraisal rights under certain circumstances, we urge you to read the summary of appraisal rights contained in this joint proxy statement/prospectus under the section entitled "The Merger—Appraisal Rights," as well as Section 262 of the DGCL, which is attached hereto as Annex F. If you wish to preserve the ability to exercise appraisal rights, you must make a written demand for appraisal of your shares as described in the section entitled "The Merger—Appraisal Rights" and in DGCL Section 262.

Litigation Related to the Merger (See page 134)

        In connection with the merger, beginning on July 21, 2014, seven putative class action lawsuits were filed in the Court of Chancery of the State of Delaware by purported URS stockholders: Falato v. URS Corp., et al., Case No. 9921; City of Atlanta Firefighters' Pension Fund v. Creel, et al., Case No. 9924; Petroutson v. URS Corp., et al., Case No. 9938; Miller v. URS Corp., et al., Case No. 9939; Oklahoma Police Pension & Retirement System v. Creel, et al., Case No. 9975; Cambridge Retirement System v. Creel, et al., Case No. 9998; Sheet Metal Workers Local No. 33 Cleveland District Pension Plan v. URS Corp., et al., Case No. 9999. The actions named as defendants URS, the members of the URS board of directors, AECOM, Merger Sub, and Merger Sub I. Two of the actions also named as a defendant JANA Partners LLC. The complaints alleged, among other things, that some or all members of the URS board of directors breached their fiduciary duties by approving the merger, and that the other defendants aided and abetted those alleged breaches. The complaints sought, among other relief, class certification, preliminary and permanent injunctive relief, and damages.

        On August 5, 2014, the Delaware Court denied the motion for expedited proceedings made by plaintiffs in the first six actions, other than the Sheet Metal Workers action. On August 28, 2014, the plaintiffs in the first six actions filed a notice of voluntary dismissal of their actions, which also indicated that plaintiffs' counsel intended to apply for an award of attorneys' fees and reimbursement of expenses.

        On August 21, 2014, plaintiff in the Sheet Metal Workers action filed an amended class action complaint that asserted breach of fiduciary duties claims against the members of the URS board of directors, and claims of aiding and abetting those alleged breaches against AECOM, Merger Sub, Merger Sub I, JANA Partners LLC, and BAML. Plaintiff also filed a motion for expedited proceedings and discovery. At a hearing on August 28, 2014, the Delaware Court denied the motion for expedited proceedings and discovery in the Sheet Metal Workers action. On September 3, 2014, the plaintiff in Sheet Metal Workers filed a notice of voluntary dismissal.

Listing of AECOM Shares; Delisting and Deregistration of Shares of URS Common Stock (See page 130)

        It is a condition to the completion of the merger that the shares of AECOM common stock to be issued to URS stockholders pursuant to the merger be authorized for listing on the NYSE at the effective time of the merger, subject to official notice of issuance. Upon completion of the merger, shares of URS common stock currently listed on the NYSE will cease to be listed on the NYSE and will subsequently be deregistered under the Exchange Act.

        See the sections entitled "The Merger—Listing of AECOM Shares" and "The Merger—Delisting and Deregistration of URS Common Stock" for a further discussion of the listing of AECOM shares and de-listing of URS common stock in connection with the merger.

The Merger Will Generally Be Tax-Free to Holders of URS Common Stock Who Receive Only AECOM Common Stock and Taxable to Holders Who Receive Cash (See page 164)

        Neither AECOM nor URS will be required to complete the merger unless it receives a legal opinion to the effect that the mergers, taken together, will qualify as a "reorganization" within the meaning of Section 368(a) of the Code. Accordingly, we expect the transaction to generally be tax-free to holders of URS common stock for United States federal income tax purposes to the extent that such holders receive only shares of AECOM common stock pursuant to the merger. Those holders receiving solely cash for their URS common stock will generally recognize gain or loss equal to the difference between the amount of cash received and their tax basis in their shares of URS common stock. Those holders receiving both AECOM common stock and cash for their URS common stock will generally recognize gain, but not loss, equal to the lesser of (1) the amount of cash received and (2) the excess of the "amount realized" in the transaction (i.e., the fair market value of the AECOM common stock at the effective time of the merger plus the amount of cash received) over their tax basis in their URS common stock. In certain circumstances, such gain or, in the case of recipients of cash only, the entire amount of cash received, could be taxable as a dividend rather than capital gain. For a further summary of the United States federal income tax consequences of the merger to holders of URS common stock, please see "Material U.S. Federal Income Tax Consequences."

        The U.S. federal income tax consequences described above may not apply to all holders of URS common stock. Your tax consequences will depend on your individual situation. Accordingly, we strongly urge you to consult your tax advisor for a full understanding of the particular tax consequences of the merger to you.

The Meetings

The AECOM Special Meeting (See page 42)

        The AECOM special meeting will be held at AECOM's headquarters, located at 1999 Avenue of the Stars, Suite 2600, Los Angeles, California 90067, on October 16, 2014, at 8:30 a.m., California time, to consider and vote upon the following matters:

•

the stock issuance proposal; and



•

the AECOM adjournment proposal.

        Completion of the merger is conditioned on, among other things, approval of the stock issuance proposal.

        The approval of the stock issuance proposal requires the affirmative vote of holders of a majority of the AECOM common stock, present in person or represented by proxy, at the AECOM special meeting and entitled to vote on the proposal, assuming a quorum is present. Approval of the AECOM adjournment proposal requires the affirmative vote of the holders of a majority of the shares of AECOM common stock entitled to vote and present in person or represented by proxy at the AECOM special meeting, whether or not a quorum is present.

        Only holders of record of AECOM common stock at the close of business on September 12, 2014, the AECOM record date, are entitled to notice of, and to vote at, the AECOM special meeting or any adjournments or postponements thereof. At the close of business on the AECOM record date, 99,541,568 shares of AECOM common stock were issued and outstanding, approximately 2.03% of which were held by AECOM's directors and executive officers and their affiliates. We currently expect that AECOM's directors and executive officers will vote their shares in favor of each of the proposals

to be considered and voted upon at the AECOM special meeting, although no director or executive officer has entered into any agreement obligating him or her to do so.

        Under the merger agreement, AECOM may, without the prior consent of URS, postpone or adjourn its special meeting to a date that is no later than 10 business days after October 16, 2014 (but prior to the date that is two business days prior to the end date) if (i) as of October 16, 2014, there are insufficient shares of AECOM common stock represented (either in person or by proxy) to constitute a quorum necessary to conduct the business of the AECOM special meeting, (ii) after consultation with URS, if the failure to adjourn or postpone the AECOM special meeting would reasonably be expected to be a violation of applicable law for the distribution of any required supplement or amendment to this joint proxy statement/prospectus, (iii) after consultation with URS, to solicit additional proxies if necessary to obtain the approval of the stock issuance proposal or (iv) AECOM has delivered to URS a bona fide written notice of its intention to make an adverse recommendation change or terminate the merger agreement in response to a superior proposal. In addition, URS may require AECOM to adjourn, delay or postpone the AECOM special meeting once for a period not to exceed 30 calendar days after October 16, 2014 (but prior to the date that is two business days prior to the end date) to solicit additional proxies necessary to obtain approval of the stock issuance proposal.

        The AECOM Board of Directors has unanimously approved the merger agreement and determined that the merger agreement and the transactions contemplated thereby, including the merger and the stock issuance, are advisable and in the best interests of AECOM and its stockholders. The AECOM Board of Directors unanimously recommends that AECOM stockholders vote "FOR" the stock issuance and "FOR" the AECOM adjournment proposal. See "The AECOM Special Meeting" for further discussion of the AECOM special meeting.

The URS Special Meeting (See page 49)

        The URS special meeting will be held at 600 Montgomery Street, 26th Floor, San Francisco, California 94111, on October 16, 2014, at 10:00 a.m., California time, to consider and vote upon the following matters:

•

the proposal to adopt the merger agreement;



•

the URS adjournment proposal; and



•

the advisory vote on the golden parachute proposal.

        Completion of the merger is conditioned on, among other things, adoption of the merger agreement.

        Adoption of the merger agreement requires the affirmative vote of the holders of a majority of the outstanding shares of URS common stock as of the record date for the URS special meeting. Approval of the URS adjournment proposal requires the affirmative vote of the holders of a majority of the shares of URS common stock entitled to vote and present in person or represented by proxy at the URS special meeting, whether or not a quorum is present. Approval of the golden parachute proposal requires the affirmative vote of holders of a majority of the shares of URS common stock present in person or represented by proxy at the URS special meeting and entitled to vote thereon, assuming a quorum is present. Neither approval of the URS adjournment proposal nor the golden parachute proposal is a condition to completion of the merger.

        Only holders of record of URS common stock at the close of business on September 12, 2014, the URS record date, are entitled to notice of, and to vote at, the URS special meeting or any adjournments thereof. At the close of business on the URS record date, 69,121,955 shares of URS common stock were issued and outstanding, approximately 0.93% of which were held by URS's directors and executive officers and their affiliates. We currently expect that URS's directors and executive officers will vote their shares in favor of each of the proposals to be considered and voted

upon at the URS special meeting, although no director or executive officer has entered into any agreement obligating him or her to do so.

        Under the merger agreement, URS may, without the prior consent of AECOM, postpone or adjourn its special meeting to a date that is no later than 10 business days after October 16, 2014 (but prior to the date that is two business days prior to the end date) if (i) as of October 16, 2014, there are insufficient shares of URS common stock represented (either in person or by proxy) to constitute a quorum necessary to conduct the business of the URS special meeting, (ii) after consultation with AECOM, if the failure to adjourn or postpone the URS special meeting would reasonably be expected to be a violation of applicable law for the distribution of any required supplement or amendment to this joint proxy statement/prospectus, (iii) after consultation with AECOM, to solicit additional proxies if necessary to obtain the approval of the proposal to adopt the merger agreement or (iv) URS has delivered to AECOM a bona fide written notice of its intention to make an adverse recommendation change or terminate the merger agreement in response to a superior proposal. In addition, AECOM may require URS to adjourn, delay or postpone the URS special meeting once for a period not to exceed 30 calendar days after October 16, 2014 (but prior to the date that is two business days prior to the end date) to solicit additional proxies necessary to obtain approval of the proposal to adopt the merger agreement.

        The URS Board of Directors has unanimously approved and adopted the merger agreement and determined that the merger agreement and the transactions contemplated thereby, including the merger, are advisable and in the best interests of URS and its stockholders. The URS Board of Directors unanimously recommends that URS stockholders vote "FOR" the adoption of the merger agreement, "FOR" the URS adjournment proposal and "FOR" the golden parachute proposal. See "The URS Special Meeting" for further discussion of the URS special meeting.

Comparison of Stockholders' Rights (See page 186)

        URS stockholders, whose rights are currently governed by the restated certificate of incorporation of URS (the "URS charter") and the amended URS bylaws (the "URS bylaws") will, to the extent such holders receive AECOM common stock in the merger, upon completion of the merger, become stockholders of AECOM and their rights will be governed by the amended and restated certificate of incorporation of AECOM (the "AECOM charter") and the amended and restated bylaws of AECOM (the "AECOM bylaws"). In general, the rights of URS's stockholders are very similar to the rights of AECOM's stockholders. The principal differences are that (i) AECOM stockholders are expressly prohibited from acting by written consent, whereas URS stockholders are permitted to take action by written consent, (ii) a business combination of AECOM requires approval of a supermajority of AECOM common stock, while only majority approval of URS common stock is required, and (iii) the AECOM Board of Directors is currently classified (though such classification is being phased out and all directors will be elected on an annual basis commencing at the 2017 annual stockholder meeting) while the URS Board of Directors is not classified. The differences between the URS governing documents and the AECOM governing documents are described in more detail under "Comparison of Stockholders' Rights."

Dividends (See page 129)

        Under the terms of the merger agreement, URS is generally prohibited from paying dividends on its common stock during the pendency of the merger. However, URS is permitted to pay to its common stockholders regular quarterly dividends consistent with past practice.

        AECOM is also generally prohibited from paying dividends on its common stock during the pendency of the merger. See "The Merger—Dividends" for further discussion on the ability of the parties to issue dividends.

Comparative Per Share Market Price Information

        The following table presents the closing prices of AECOM common stock and URS common stock on the NYSE on July 11, 2014, the last trading day before announcement of the merger, and September 12, 2014, the most recent practicable date prior to the date of this joint proxy statement/prospectus. The table also presents the closing sales prices calculated by averaging the closing sales prices for shares of AECOM common stock on each of the trading days during the period of five trading days ending on such dates. The table also presents the approximately equivalent value of the per share merger consideration of URS common stock on those dates, calculated by multiplying the average five-day closing price of AECOM common stock ending on those dates by 0.734 and adding $33.00, representing the approximate value that URS stockholders will be entitled to receive in exchange for each share of URS common stock they hold at the effective time of the merger, assuming no proration.

        The market prices of shares of AECOM and URS common stock fluctuate. The value of the merger consideration will fluctuate with the market price of the AECOM common stock and will be determined based on the average five-day AECOM closing price. As a result, we urge you to obtain current market quotations of AECOM and URS common stock.

Summary Consolidated Historical Financial Data of AECOM

        The following table sets forth selected historical consolidated financial data of AECOM. This data is derived from AECOM's consolidated financial statements as of and for the five years ended September 30, 2013, 2012, 2011, 2010 and 2009, respectively, and the unaudited quarterly financial statements as of and for the nine months ended June 30, 2014 and 2013, which in the opinion of management include all adjustments necessary for a fair statement of the results for the unaudited interim periods. AECOM reports results of operations based on 52- or 53-week periods ending on the Friday nearest September 30. For clarity of presentation, all periods are presented as if the year ended on September 30. Fiscal years 2013, 2012, 2011, 2010 and 2009 each contained 52 weeks and ended on September 27, September 28, September 30, September 30, October 1 and October 2, respectively. This selected financial data should be read in conjunction with AECOM's consolidated financial statements and related notes included in AECOM's Annual Report on Form 10-K for the fiscal year ended September 30, 2013, and AECOM's quarterly report on Form 10-Q for the quarter ended June 30, 2014, each of which is incorporated by reference in this joint proxy statement/prospectus. See "Where You Can Find More Information."