TETRA TECH INC

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a later dated paper proxy; (3) delivering to our Corporate Secretary a written notice of revocation prior to the voting of the proxy at the 2026 Annual Meeting; or (4) voting in person at the 2026 Annual Meeting. Simply attending the 2026 Annual Meeting will not revoke your proxy. Any change to your proxy provided by telephone or via the internet must be submitted by 11:59 p.m. Eastern Time on February 18, 2026.

If your shares are held in street name, you may change your vote by submitting new voting instructions to your nominee. You must contact your nominee to find out how you can change your vote.

Quorum and Votes Required

Votes cast by proxy or in person at the 2026 Annual Meeting will be tabulated by Broadridge Financial Solutions, Inc., the independent agent appointed as inspector of election by our Board. The inspector of election will also determine whether a quorum is present.

At the 2026 Annual Meeting, the existence of a quorum and tabulation of votes is determined as follows:

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The presence in person or representation by proxy of a majority of the outstanding shares of common stock on the record date and entitled to vote at the 2026 Annual Meeting shall constitute a quorum for the transaction of business. Shares represented by proxies that reflect abstentions or “broker nonvotes” ​(which are shares held by a nominee that are represented and voted on a routine matter at the meeting, but with respect to which the nominee is not empowered to vote on another nonroutine matter at the meeting) will be counted as shares that are present and entitled to vote at the 2026 Annual Meeting for purposes of determining the presence of a quorum. The items scheduled to be considered at the 2026 Annual Meeting all are “nonroutine” under the applicable rules, except for Item 4, ratification of appointment of our independent registered public accounting firm. Nominees are prohibited from voting on nonroutine items in the absence of instructions from the beneficial owners of the shares. As a result, if you hold your shares in street name and do not submit voting instructions to your nominee, your shares will be voted on Item 4 in the manner directed by your nominee, but will not be voted on Item 1, election of directors; Item 2, advisory vote to approve our named executive officers’ compensation; and Item 3, approval of the amendment to the ESPP to increase the number of shares of common stock authorized for issuance over the term of the ESPP by 10,000,000 shares, and will constitute broker nonvotes on each such item. We urge you to promptly provide voting instructions to your nominee so that your vote is counted for Item 1, Item 2, and Item 3.

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Because there is no cumulative voting and this is an uncontested election, each of the director nominees named in Item 1 receiving a majority of the votes cast will be elected as a director (for these purposes, “a majority of votes cast” means that the number of shares voted “for” a director’s election exceeds the number of shares voted “against” that director’s election). Abstentions and broker nonvotes will not count as a vote cast for or against a nominee’s election and, therefore, will have no effect in determining whether a director nominee has received a majority of the votes cast.

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For Item 2, advisory vote to approve our named executive officers’ compensation; Item 3, approval of the amendment to the ESPP to increase the number of shares of common stock authorized for issuance over the term of the ESPP by 10,000,000 shares; and Item 4, ratification of appointment of our independent registered public accounting firm, the affirmative vote of the majority of the shares represented at the 2026 Annual Meeting and entitled to vote on the item will be the act of the stockholders. Abstentions as to a particular item will have the same effect as a vote against that item. Broker nonvotes will have no effect on the vote for Item 2 and Item 3. Ratifying the appointment of our independent registered public accounting firm is considered a routine matter on which brokers may vote in their discretion on behalf of beneficial owners. Accordingly, broker nonvotes should not be applicable to Item 4. Also, Item 2 and Item 4 are advisory only and are not binding on our Company. Our Board of Directors will consider the outcome of the vote on each of these items in considering what action, if any, should be taken in response to the advisory vote by stockholders.

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Vote Results

We intend to announce preliminary voting results at the conclusion of the 2026 Annual Meeting. We expect to report final voting results in a Current Report on Form 8-K filed with the SEC on or before four business days following the 2026 Annual Meeting.

Proxy Solicitation

Tetra Tech will bear all costs related to this solicitation of proxies. Some of our employees may solicit proxies in person, by telephone, or by email; those employees will not receive any additional compensation for their proxy solicitation efforts. We will reimburse banks, brokers, and other custodians, nominees, and fiduciaries for reasonable out of pocket expenses they incur in forwarding our proxy materials to beneficial stockholders. You can help reduce these costs by electing to access proxy materials electronically.

Tetra Tech 2026 Proxy Statement 76