UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported):

October 7, 2025

TETRA TECH, INC.

(Exact name of registrant as specified in its charter)

Delaware

0-19655

95-4148514

(State or other jurisdiction
of incorporation)

(Commission
File Number)

(IRS Employer

Identification Number)

3475 East Foothill Boulevard, Pasadena, California 91107

(Address of principal executive office, including zip code)

(626) 351-4664

(Registrant’s telephone number, including area code)

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

¨	Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

¨	Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

¨	Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

¨	Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading symbol(s)		Name of each exchange on which registered
Common Stock, $0.01 par value		TTEK		The Nasdaq Stock Market LLC

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging Growth Company ¨

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

Item 5.02.

Departure of Directors or Principal Officers; Election of Directors; Appointment of Principal Officers.

Appointment of Officer

On October 7, 2025, Tetra Tech, Inc. (the “Company”) announced that Roger R. Argus, Executive Vice President, Corporate Development, and President, Commercial/International Services Group, has been promoted to serve as the Company’s President, reporting to Dan L. Batrack, Chairman and Chief Executive Officer. In this role, Mr. Argus will oversee the Company’s global operations, working closely with senior leadership and operational teams to sustain the Company’s exceptional performance and strategic growth.

Mr. Argus joined Tetra Tech more than 30 years ago, and has held increasingly responsible positions. He has served as Executive Vice President, Corporate Development since November 2024, and President, Commercial/International Services Group since October 2023. Prior to this, Mr. Argus served as Senior Vice President and President, Government Services Group from October 2018 to October 2024, and President, U.S. Government Division from October 2017 to November 2024. During his tenure with the Company, he also served as project and program manager and business unit leader. He holds a Bachelor of Science in Chemical Engineering from California State University, Long Beach.

Item 8.01.

Other Events.

On October 7, 2025, the Company issued a press release announcing the matters described in Item 5.02. A copy of the press release is attached as Exhibit 99.1 and is incorporated by reference herein.

Item 9.01.

Financial Statements and Exhibits.

(d)

Exhibits

	99.1	Press Release, dated October 7, 2025.

	104	Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

	TETRA TECH, INC.

Date: October 7, 2025	By:	/s/ Dan L. Batrack
		Dan L. Batrack
		Chairman and Chief Executive Officer

TETRA TECH INC 8-K