Form 8-K

8-K — TETRA TECH INC

Accession: 0001104659-26-106564

Filed: 2026-09-10

Period: 2026-09-10

CIK: 0000831641

SIC: 8711 (SERVICES-ENGINEERING SERVICES)

Item: Other Events

Item: Financial Statements and Exhibits

Documents

8-K — tm2625143d1_8k.htm (Primary)

EX-99.1 — EXHIBIT 99.1 (tm2625143d1_ex99-1.htm)

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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):

September

10, 2026

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 ¨

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 8.01. Other Events.

On September 10,

2026, Tetra Tech announced that its Board of Directors has authorized a $500 million increase to its share repurchase program. A

copy of the press release is attached to this Current Report as Exhibit 99.1.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits

99.1 Press Release, dated September 10, 2026, announcing Tetra Tech’s Board of Directors authorized

a $500 million increase to its share repurchase program.

104 Cover Page Interactive Data File (embedded

within the Inline XBRL document)

SIGNATURES

Pursuant to the requirements

of the Securities Exchange Act of 1934, Tetra Tech has duly caused this report to be signed on its behalf by the undersigned hereunto

duly authorized.

TETRA TECH, INC.

Date: September 10, 2026

By:

/s/ ROGER R. ARGUS

Roger R. Argus

Chief Executive Officer and President

EX-99.1 — EXHIBIT 99.1

EX-99.1

Filename: tm2625143d1_ex99-1.htm · Sequence: 2

Exhibit 99.1

NEWS

RELEASE

September 10, 2026

Tetra Tech Announces

$500 Million Increase to its Share Repurchase Program

Pasadena,

California. Tetra Tech, Inc. (NASDAQ: TTEK), a global provider of high-end technical and engineering

services, Leading with Science® in water, environment and sustainable infrastructure, announced

today that its Board of Directors approved an addtional $500 million share repurchase authorization. This more than

doubles the amount remaining under the Company’s existing share repurchase program at the end of the third quarter of

fiscal 2026, increasing total available share repurchases to $898 million.

For the twelve

months ended the third quarter of fiscal 2026, Tetra Tech generated $567 million in cash flow from operations and returned $322 million

to shareholders through share repurchases and dividends. During this period, the Company also advanced its Leading with Science®

differentiation with the completion of strategic acquisitions that added new clients and technical capabilities. The strong cash flow

also enabled the Company to continue deleveraging its balance sheet, and its net debt leverage ratio was 0.88x at the end of third quarter

2026.

“The increased share repurchase program

reflects confidence in Tetra Tech’s long-term growth outlook and our balanced approach to capital allocation,” said Roger

Argus, Tetra Tech Chief Executive Officer. “Our more than 20-year track record of generating cash from operations in excess of

net income enables us to continue investing in organic growth initiatives and strategic acquisitions, while the new

authorization expands our capacity to return capital to shareholders.”

About Tetra Tech

Tetra Tech

is the leader in water, environment and sustainable infrastructure, providing high-end technical and engineering services for projects

worldwide. With more than 25,000 employees working together, Tetra Tech provides clear solutions to complex problems by Leading with

Science® to address the entire water cycle, protect and restore the environment, and design sustainable and resilient

infrastructure. For more information about Tetra Tech, please visit tetratech.com or follow us on LinkedIn and Facebook.

CONTACTS:

Jim Wu, Investor Relations

Charlie MacPherson, Media & Public Relations

(626) 470-2844

Any statements

made in this release that are not based on historical fact are forward-looking statements. Any forward-looking statements

made in this release represent management’s best judgment as to what may occur in the future. However, Tetra Tech’s

actual outcome and results are not guaranteed and are subject to certain risks, uncertainties and assumptions ("Future Factors"),

and may differ materially from what is expressed. For a description of Future Factors that could cause actual results to differ

materially from such forward-looking statements, see the discussion under the section "Risk Factors" included in the Company’s

Form 10-K and Form 10-Q filings with the Securities and Exchange Commission.

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