UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 14A
Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No.     )
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Tetra Tech, Inc.
(Name of Registrant as Specified In Its Charter)
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*** Exercise Your Right to Vote *** Important Notice Regarding the Availability of Proxy Materials for the Stockholder Meeting to Be Held on February 24, 2021 TETRA TECH, INC. Date: February 24, 2021 Time: 10:00 AM PST 3475 East Foothill Blvd You are receiving this communication because you hold shares in the above named company. This is not a ballot. You cannot use this notice to vote these shares. This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. You may view the proxy materials online at www.proxyvote.com or easily request a paper copy (see reverse side). We encourage you to access and review all of the important information contained in the proxy materials before voting. 1234567 1234567 Envelope # # of # Sequence # 1 OF 2 12 15 0000478042_1 R1.0.1.18 Broadridge Internal Use Only Job # Sequence # See the reverse side of this notice to obtain proxy materials and voting instructions. TETRA TECH, INC. C/O COMPUTERSHARE P.O. BOX 43070 PROVIDENCE, RI 02940-3070 Investor Address Line 1 Investor Address Line 2 Investor Address Line 3 Investor Address Line 4 Investor Address Line 5 John Sample 1234 ANYWHERE STREET ANY CITY, ON A1A 1A1 1234567 1234567 1234567 234567 Meeting Information Meeting Type: Annual Meeting For holders as of: December 30, 2020 Location: Tetra Tech, Inc. Pasadena, CA 91107 B A R C O D E

Before You Vote How to Access the Proxy Materials Proxy Materials Available to VIEW or RECEIVE: Have the information that is printed in the box marked by the arrow (located on the by the arrow (located on the following page) in the subject line. How To Vote Please Choose One of the Following Voting Methods marked by the arrow available and follow the instructions. Only 0000478042_2 R1.0.1.18 Vote In Person: Many stockholder meetings have attendance requirements including, but not limited to, the possession of an attendance ticket issued by the entity holding the meeting. Please check the meeting materials for any special requirements for meeting attendance. At the meeting, you will need to request a ballot to vote these shares. Vote By Internet: To vote now by Internet, go to www.proxyvote.com. Have the information that is printed in the box Vote By Mail: You can vote by mail by requesting a paper copy of the materials, which will include a proxy card. Internal Use 1. Notice & Proxy Statement2. Annual Report3. Shareholder Letter How to View Online: following page) and visit: www.proxyvote.com. How to Request and Receive a PAPER or E-MAIL Copy: If you want to receive a paper or e-mail copy of these documents, you must request one. There is NO charge for requesting a copy. Please choose one of the following methods to make your request: 1) BY INTERNET:www.proxyvote.com 2) BY TELEPHONE:1-800-579-1639 3) BY E-MAIL*:sendmaterial@proxyvote.com * If requesting materials by e-mail, please send a blank e-mail with the information that is printed in the box marked Requests, instructions and other inquiries sent to this e-mail address will NOT be forwarded to your investment advisor. Please make the request as instructed above on or before February 10, 2021 to facilitate timely delivery.

The Board of Directors recommends you vote FOR the following: 1. 1A Election of Directors Nominees Dan L. Batrack 1B Gary R. Birkenbeuel 1C Patrick C. Haden 1D J. Christopher Lewis 1E Joanne M. Maguire 1F Kimberly E. Ritrievi 1G J. Kenneth Thompson 1H Kirsten M. Volpi The Board of Directors recommends you vote FOR proposals 2 and 3. 2To approve, on an advisory basis, the Company's executive compensation; 3To ratify the appointment of PricewaterhouseCoopers LLP as the Company's independent registered public accounting firm for fiscal year 2021. NOTE: In their discretion, the proxies are authorized to vote on such other business as may properly come before the meeting or any postponement or adjournment thereof. xxxxxxxxxx Sequence # 0000478042_3 R1.0.1.18 Broadridge Internal Use Only xxxxxxxxxx Cusip Job # Envelope # # of # Sequence # B A R C O D E 23456789012 2 2 2 2 12345678901 12345678901 12345678901 12345678901 12345678901 12345678901 12345678901 12345678901 12345678901 12345678901 Voting items

THE COMPANY NAME INC. - CLASS A THE COMPANY NAME INC. - CLASS C 123,456,789,012.12345 123,456,789,012.12345 THE COMPANY NAME INC. - CLASS F 123,456,789,012.12345 Envelope # # of # Sequence # 0000478042_4 R1.0.1.18 Broadridge Internal Use Only THIS SPACE RESERVED FOR SIGNATURES IF APPLICABLE Job # Sequence # NAME THE COMPANY NAME INC. - COMMON 123,456,789,012.12345 THE COMPANY NAME INC. - CLASS B123,456,789,012.12345 THE COMPANY NAME INC. - CLASS D123,456,789,012.12345 THE COMPANY NAME INC. - CLASS E123,456,789,012.12345 THE COMPANY NAME INC. - 401 K123,456,789,012.12345 Reserved for Broadridge Internal Control Information