EXHIBIT 99.1 Exhibit 99.1 NEWS RELEASE November 12, 2025 Tetra Tech Reports Strong Fourth Quarter and Fiscal 2025 Results · Fourth Quarter 2025 Results ‒ Record Net Revenue $1.16 billion ‒ Record Operating Income of $181 million, up 26% Y/Y ‒ Record EPS $0.48, up 37% Y/Y · Fiscal 2025 Results ‒ Record Annual Revenue $5.44 billion ‒ Record Annual Net Revenue $4.62 billion ‒ Annual EPS $0.93; Record Adjusted Annual EPS $1.56, up 24% Y/Y ‒ Record Operating Cash Flow $458 million, up 28% Y/Y Pasadena, California . Tetra Tech, Inc. (NASDAQ: TTEK), a leading provider of high-end consulting and engineering services in water, environment and sustainable infrastructure, today announced results for the fourth quarter and fiscal year ended September 28, 2025. Fourth Quarter 2025 Highlights (Excluding USAID and Dept. of State (DOS)) · Revenue increased 6% Y/Y to $1.23 billion · Net Revenue 1 increased 10% Y/Y to $1.07 billion · Adjusted 1 Operating Income increased 23% Y/Y to $168 million · Adjusted EPS increased 29% Y/Y to $0.44 Fiscal 2025 Highlights (Excluding USAID and DOS) · Revenue increased 9% Y/Y to $4.79 billion 1 Non-GAAP financial measures which the Company believes provide valuable perspectives on its business results. Refer to tables at the end of the release and Regulation G Information for reconciliations to the comparable GAAP metrics. · Net Revenue increased 10% Y/Y to $4.06 billion · Adjusted Operating Income increased 24% Y/Y to $563 million · Adjusted EPS increased 31% Y/Y to $1.45 Recent Key Wins · $500 million multiple-award contract for environmental services for USACE Baltimore District · $249 million multiple-award contract for planning and engineering services for USACE Mobile District · $240 million single-award contract for environmental assessment services for U.S. Navy · $240 million multiple-award contract for planning and engineering services for USACE Norfolk District · $38 million multiple-award contract for transmission and distribution services for an Irish grid operator · $23 million single-award contract for water engineering services for Portsmouth Water in the U.K. · $18 million single-award contract for high-voltage energy design services for a U.S. commercial client Quarterly Dividend and Share Repurchase Program On November 10, 2025, Tetra Tech’s Board of Directors approved the Company’s 46 th consecutive quarterly dividend at an amount of $0.065 per share, a 12% increase year-over-year, payable on December 12, 2025, to stockholders of record as of December 1, 2025. In the fourth quarter, Tetra Tech repurchased $50 million of common stock. Additionally, as of September 28, 2025, the Company had $598 million remaining under the approved share repurchase programs. Executive Management Comments Dan Batrack, Chairman and CEO, commented, “We finished fiscal 2025 with another strong quarter resulting in record net revenue, record operating income, and significant operating margin expansion. These all-time high results were driven by the continued strong demand for our differentiated high-end consulting services in resilient water management and digital water automation. Our strategy focused on essential water and environmental services has allowed us to successfully navigate the recent changes in U.S. federal government priorities as we achieved record financial performance for 2025.” Roger Argus, President, stated, “Looking forward to fiscal 2026 and beyond, we see increased demand for our high-end services to address the development of water-reliant infrastructure, including data centers and industrial manufacturing. Our high-voltage engineering practice has benefited from these projects with its backlog doubling in the fourth quarter. In addition, our front-end consulting services are critical to the expansion and protection of coastal and marine infrastructure for defense clients around the world.” Business Outlook The following statements are based on current expectations. These statements are forward-looking, and the actual results could differ materially. These statements do not include the potential impact of transactions that may be completed or developments that become evident after the date of this release. The Business Outlook section should be read in conjunction with the information on forward-looking statements at the end of this release. For fiscal 2026, Tetra Tech expects net revenue 2 to range from $4.05 billion to $4.25 billion and EPS guidance to range from $1.40 to $1.55. The fiscal 2026 guidance for net revenue projects a range of 5% to 11% year-over-year growth, excluding fiscal 2025 USAID / DOS and episodic disaster recovery activities. For the first quarter of fiscal 2026, Tetra Tech expects net revenue to range from $950 million to $1.0 billion and EPS to range from $0.30 to $0.33. 2 Reconciliation of the net revenue guidance to the most directly comparable GAAP measure is not available without unreasonable efforts because the Company cannot predict the magnitude and timing of all the components, including subcontractor costs, required to provide such reconciliation with sufficient precision. 2 Webcast Investors will have the opportunity to access a live audio-visual webcast and supplemental financial information concerning the fourth quarter of fiscal 2025 results through a link posted on the Company’s website at tetratech.com on November 13, 2025, at 8:00 a.m. (PT). Reconciliation of GAAP and Non-GAAP Items In thousands (except EPS data) Three Months Ended Fiscal Year Ended Sep. 28, 2025 Sep. 29, 2024 Sep. 28, 2025 Sep. 29, 2024 Revenue $ 1,330,100 $ 1,374,474 $ 5,442,590 $ 5,198,679 USAID / DOS (97,771 ) (215,267 ) (650,344 ) (793,029 ) Revenue excl. USAID / DOS $ 1,232,329 $ 1,159,207 $ 4,792,246 $ 4,405,694 Revenue $ 1,330,100 $ 1,374,474 $ 5,442,590 $ 5,198,679 Subcontractor costs (166,791 ) (229,989 ) (825,230 ) (876,817 ) Net revenue $ 1,163,309 $ 1,144,485 $ 4,617,360 $ 4,321,862 USAID / DOS (91,351 ) (174,379 ) (555,456 ) (644,672 ) Net revenue excl. USAID / DOS $ 1,071,958 $ 970,106 $ 4,061,904 $ 3,677,190 Operating Income $ 181,305 $ 143,343 $ 408,419 $ 500,737 Contingent consideration (9,873 ) 2,064 (12,228 ) 2,541 Legal contingency - - 115,000 - Goodwill impairment - - 92,416 - Acq. / Integration - 7,138 - 7,138 Adjusted Operating Income $ 171,432 $ 152,545 $ 603,607 $ 510,416 USAID / DOS (3,795 ) (16,063 ) (40,433 ) (55,497 ) Adjusted OI excl. USAID / DOS $ 167,637 $ 136,482 $ 563,174 $ 454,919 EPS $ 0.48 $ 0.35 $ 0.93 $ 1.23 Contingent consideration (0.03 ) 0.01 (0.03 ) 0.01 Legal contingency - - 0.35 - Goodwill impairment - - 0.31 - Acq. / Integration - 0.02 - 0.02 Adjusted EPS $ 0.45 $ 0.38 $ 1.56 $ 1.26 USAID / DOS (0.01 ) (0.04 ) (0.11 ) (0.15 ) Adj. EPS excl. USAID / DOS $ 0.44 $ 0.34 $ 1.45 $ 1.11 3 About Tetra Tech Tetra Tech is the leader in water, environment and sustainable infrastructure, providing high-end consulting 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 Forward-Looking Statements This release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. The use of words such as "anticipate," "expect," "could," "may," "intend," "plan" and "believe," among others, generally identify forward-looking statements. These forward-looking statements are based on current expectations and beliefs of Tetra Tech’s management and currently available operating, financial, economic and other information, and are subject to a number of risks and uncertainties. Readers are cautioned that these forward-looking statements are only predictions and may differ materially from actual future events or results. A variety of factors, many of which are beyond our control, could cause actual future results or events to differ materially from those projected in the forward-looking statements in this release, including but not limited to: continuing worldwide political and economic uncertainties; the U.S. Administration’s potential changes to fiscal policies; the cyclicality in demand for our overall services; the fluctuation in demand for oil and gas, and mining services; risks related to international operations; concentration of revenues from U.S. government agencies and potential funding disruptions by these agencies; dependence on winning or renewing U.S. government contracts; the delay or unavailability of public funding on U.S. government contracts; the U.S. government’s right to modify, delay, curtail or terminate contracts at its convenience; compliance with government procurement laws and regulations; the impact of global pandemics; credit risks associated with certain clients in certain geographic areas or industries; acquisition strategy and integration risks; goodwill or other intangible asset impairment; the failure to comply with worldwide anti-bribery laws; the failure to comply with domestic and international export laws; the failure to properly manage projects; the loss of key personnel or the inability to attract and retain qualified personnel; the ability of our employees to obtain government granted eligibility; the use of estimates and assumptions in the preparation of financial statements; the ability to maintain adequate workforce utilization; the use of the percentage-of-completion method of accounting; the inability to accurately estimate and control contract costs; the failure to adequately recover on our claims for additional contract costs; the failure to win or renew contracts with private and public sector clients; growth strategy management; backlog cancellation and adjustments; risks relating to cyber security breaches; the failure of partners to perform on joint projects; the failure of subcontractors to satisfy their obligations; requirements to pay liquidated damages based on contract performance; the adoption of new legal requirements; changes in resource management, environmental or infrastructure industry laws, regulations or programs; changes in bank and capital markets and the access to capital; credit agreement covenants; industry competition; liability related to legal proceedings, investigations, and disputes; the availability of third-party insurance coverage; the ability to obtain adequate bonding; employee, agent, or partner misconduct; employee risks related to international travel; safety programs; conflict of interest issues; liabilities relating to reports and opinions; liabilities relating to environmental laws and regulations; force majeure events; protection of intellectual property rights; stock price volatility; the ability to impede a business combination based on Delaware law and charter documents; and other risks and uncertainties as may be described in Tetra Tech’s periodic filings with the Securities and Exchange Commission, including those described in the “Risk Factors” section of Tetra Tech’s Annual Report on Form 10-K for the fiscal year ended September 29, 2024. Readers should not place undue reliance on forward-looking statements since such information speaks only as of the date of this release. Tetra Tech does not intend to update forward-looking statements and expressly disclaims any obligation to do so. 4 Non-GAAP Financial Measures To supplement the financial results presented in accordance with generally accepted accounting principles in the United States (“GAAP”), we present certain non-GAAP financial measures within the meaning of Regulation G under the Securities Exchange Act of 1934, as amended. We provide these non-GAAP financial measures because we believe they provide a valuable perspective on our financial results. However, non-GAAP measures have limitations as analytical tools and should not be considered in isolation and are not in accordance with, or a substitute for, GAAP measures. In addition, other companies may define non-GAAP measures differently which limits the ability of investors to compare non-GAAP measures of Tetra Tech to those used by our peer companies. A reconciliation of these non-GAAP financial measures to the most directly comparable GAAP financial measures is set forth above in this release. 5 Tetra Tech, Inc Balance Sheet - Unaudited (unaudited - in thousands, except par value) September 28, September 29, 2025 2024 Assets Current assets: Cash and cash equivalents 167,459 232,689 Accounts receivable, net 1,158,928 1,051,461 Contract assets 138,232 129,678 Prepaid expenses and other current assets 83,434 91,585 Assets held-for-sale 61,305 - Income taxes receivable 15,334 21,970 Total current assets 1,624,692 1,527,383 Property and equipment, net 66,148 73,065 Right-of-use assets, operating leases 197,618 177,950 Goodwill 2,049,874 2,046,569 Intangible assets, net 121,160 160,585 Deferred tax assets 106,238 105,529 Other non-current assets 116,444 101,595 Total assets 4,282,174 4,192,676 Liabilities and Equity Current liabilities: Accounts payable 204,725 197,440 Accrued compensation 346,912 332,096 Contract liabilities 420,254 351,738 Short-term lease liabilities, operating leases 69,099 63,419 Current contingent earn-out liabilities 24,826 26,934 Liabilities held-for-sale 28,461 - Other current liabilities 288,113 247,900 Total current liabilities 1,382,390 1,219,527 Deferred tax liabilities 21,333 30,162 Long-term debt 763,363 812,634 Long-term lease liabilities, operating leases 154,695 140,095 Non-current contingent earn-out liabilities 32,135 21,812 Other non-current liabilities 148,094 138,033 Total liabilities 2,502,010 2,362,263 Equity: Preferred stock - authorized, 2,000 shares of $0.01 par value; no shares issued and outstanding at September 28, 2025 and September 29, 2024 - - Common stock - authorized, 750,000 shares of $0.01 par value; issued and outstanding, 261,418 and 267,717 shares at September 28, 2025 and September 29, 2024, respectively 2,614 2,677 Additional paid-in capital - 35,900 Accumulated other comprehensive loss (95,777 ) (78,875 ) Retained earnings 1,872,948 1,870,620 Tetra Tech stockholders' equity 1,779,785 1,830,322 Noncontrolling interests 379 91 Total stockholders' equity 1,780,164 1,830,413 Total liabilities and stockholders' equity 4,282,174 4,192,676 6 Tetra Tech, Inc Consolidated Statements of Income (unaudited - in thousands, except per share data) Three Months Ended Fiscal Year Ended September 28, September 29, September 28, September 29, 2025 2024 2025 2024 Revenue $ 1,330,100 $ 1,374,474 $ 5,442,590 $ 5,198,679 Subcontractor costs (166,791 ) (229,989 ) (825,230 ) (876,817 ) Other costs of revenue (889,163 ) (899,209 ) (3,656,016 ) (3,455,422 ) Gross profit 274,146 245,276 961,344 866,440 Selling, general and administrative expenses (102,714 ) (92,731 ) (357,737 ) (356,024 ) Contingent consideration - fair value adjustments 9,873 (2,064 ) 12,228 (2,541 ) Legal contingency costs - - (115,000 ) - Impairment of goodwill - - (92,416 ) - Acquisition and integration expenses - (7,138 ) - (7,138 ) Income from operations 181,305 143,343 408,419 500,737 Interest expense, net (6,806 ) (7,898 ) (30,802 ) (37,271 ) Income before income tax expense 174,499 135,445 377,617 463,466 Income tax expense (46,623 ) (39,265 ) (129,668 ) (130,023 ) Net income 127,876 96,180 247,949 333,443 Net income attributable to noncontrolling interests (131 ) (26 ) (225 ) (61 ) Net income attributable to Tetra Tech $ 127,745 $ 96,154 $ 247,724 $ 333,382 Earnings per share attributable to Tetra Tech: Basic $ 0.49 $ 0.36 $ 0.94 $ 1.25 Diluted $ 0.48 $ 0.35 $ 0.93 $ 1.23 Weighted-average common shares outstanding: Basic 262,184 267,687 264,713 267,364 Diluted 264,247 271,656 267,123 270,042 Cash dividends paid per share 0.065 0.058 0.246 0.220 7 Tetra Tech, Inc. Consolidated Statements of Cash Flows (unaudited - in thousands) Fiscal Year Ended September 28, September 29, 2025 2024 Cash flows from operating activities: Net income $ 247,949 $ 333,443 Adjustments to reconcile net income to net cash provided by operating activities: Depreciation and amortization 58,276 73,677 Amortization of stock-based awards 33,946 31,155 Deferred income taxes (11,297 ) (19,980 ) Provision for losses on accounts receivables 3,150 - Impairment of goodwill 92,416 - Fair value adjustments to contingent consideration (12,228 ) 2,541 Acquisition and integration expenses - 7,138 Other non-cash items 9,024 5,369 Changes in operating assets and liabilities, net of effects of business acquisitions and divestitures: Accounts receivable and contract assets (112,755 ) (40,188 ) Prepaid expenses and other assets (30,563 ) (20,894 ) Accounts payable 2,398 18,091 Accrued compensation 18,879 6,657 Contract liabilities 73,489 4,704 Cash settled contingent earn-out liability (11,170 ) (7,943 ) Income taxes receivable/payable 23,227 (35,530 ) Other liabilities 72,944 468 Net cash provided by operating activities 457,685 358,708 Cash flows from investing activities: Payments for business acquisitions, net of cash acquired (97,263 ) (93,650 ) Capital expenditures (18,633 ) (18,135 ) Proceeds from sale of assets 919 742 Proceeds from company-owned life insurance policies 1,934 - Proceeds from divested business, net 2,406 - Proceeds from loan repayment from divested business 3,883 - Net cash used in investing activities (106,754 ) (111,043 ) Cash flows from financing activities: Proceeds from borrowings 715,000 217,000 Repayments on long-term debt (771,027 ) (287,000 ) Payment of debt issuance costs (2,738 ) - Repurchases of common stock (249,984 ) - Shares repurchased for tax withholdings on share-based awards (14,047 ) (12,982 ) Payments of contingent earn-out liabilities (15,055 ) (46,107 ) Stock options exercised 469 3,067 Dividends paid (65,039 ) (58,828 ) Principal payments on finance leases (7,823 ) (6,530 ) Net cash used in financing activities (410,244 ) (191,380 ) Effect of exchange rate changes on cash and cash equivalents (5,004 ) 7,573 Net increase (decrease) in cash and cash equivalents (64,317 ) 63,858 Cash and cash equivalents at beginning of year 232,689 168,831 Cash and cash equivalents at end of year $ 168,372 $ 232,689 Supplemental information: Cash paid during the period for: Interest $ 34,956 $ 36,855 Income taxes, net of refunds received of $17.2 million and $4.2 million $ 110,830 $ 180,707 Non-cash financing activities: Excise taxes accrued but not paid $ 2,010 $ - Reconciliation of cash and cash equivalents to consolidated balance sheets: Cash and cash equivalents $ 167,459 $ 232,689 Cash and cash equivalents included in assets held-for-sale 913 - Consolidated cash and cash equivalents $ 168,372 $ 232,689 8 Tetra Tech, Inc. Regulation G Information September 28, 2025 Reconciliation of Revenue to Revenue, Net of Subcontractor Costs ("Net Revenue") (in millions) 2024 2025 2022 2023 1st Qtr 2nd Qtr 6 Mos 3rd Qtr 9 Mos 4th Qtr Total 1st Qtr 2nd Qtr 6 Mos 3rd Qtr 9 Mos 4th Qtr Total Consolidated Revenue 3,504.0 4,522.6 1,228.3 1,251.6 2,479.9 1,344.3 3,824.2 1,374.5 5,198.7 1,420.6 1,322.1 2,742.7 1,369.8 4,112.5 1,330.1 5,442.6 Subcontractor Costs (668.5 ) (771.5 ) (213.1 ) (199.0 ) (412.1 ) (234.7 ) (646.8 ) (230.0 ) (876.8 ) (223.3 ) (218.4 ) (441.7 ) (216.8 ) (658.5 ) (166.8 ) (825.3 ) Net Revenue 2,835.5 3,751.1 1,015.2 1,052.6 2,067.8 1,109.6 3,177.4 1,144.5 4,321.9 1,197.3 1,103.7 2,301.0 1,153.0 3,454.0 1,163.3 4,617.3 GSG Segment Revenue 1,820.9 2,158.9 575.0 597.1 1,172.2 640.6 1,812.7 670.6 2,483.4 751.8 661.4 1,413.2 673.0 2,086.2 587.7 2,673.9 Subcontractor Costs (484.4 ) (523.4 ) (132.3 ) (130.6 ) (263.0 ) (152.3 ) (415.3 ) (158.1 ) (573.4 ) (150.6 ) (140.5 ) (291.1 ) (152.6 ) (443.6 ) (100.5 ) (544.1 ) Net Revenue 1,336.5 1,635.5 442.7 466.5 909.2 488.3 1,397.4 512.5 1,910.0 601.2 520.9 1,122.1 520.4 1,642.6 487.2 2,129.8 CIG Segment Revenue 1,738.4 2,424.6 669.1 671.2 1,340.3 723.6 2,063.9 722.9 2,786.7 688.2 678.9 1,367.1 715.8 2,082.8 761.9 2,844.6 Subcontractor Costs (239.3 ) (309.0 ) (96.6 ) (85.1 ) (181.7 ) (102.2 ) (283.9 ) (90.9 ) (374.8 ) (92.1 ) (96.1 ) (188.2 ) (83.2 ) (271.4 ) (85.7 ) (357.1 ) Net Revenue 1,499.1 2,115.6 572.5 586.1 1,158.6 621.4 1,780.0 632.0 2,411.9 596.1 582.8 1,178.9 632.6 1,811.4 676.2 2,487.5 Reconciliation of Net Income Attributable to Tetra Tech to Adjusted EBITDA (in thousands) 2024 2025 2022 2023 1st Qtr 2nd Qtr 6 Mos 3rd Qtr 9 Mos 4th Qtr Total 1st Qtr 2nd Qtr 6 Mos 3rd Qtr 9 Mos 4th Qtr Total Net Income Attributable to Tetra Tech 263,125 273,420 74,972 76,446 151,418 85,810 237,228 96,154 333,382 747 5,388 6,135 113,844 119,979 127,745 247,724 Income Tax Expense 85,602 127,526 26,523 31,341 57,864 32,894 90,757 39,266 130,023 14,530 25,700 40,230 42,815 83,045 46,624 129,668 Interest Expense 11,584 46,537 9,578 9,883 19,461 9,912 29,374 7,897 37,271 7,218 8,491 15,709 8,287 23,996 6,806 30,802 Depreciation 13,859 19,980 6,951 5,637 12,588 5,713 18,301 5,421 23,722 5,402 5,248 10,650 5,410 16,059 5,115 21,175 Amortization 13,174 41,226 12,533 12,094 24,627 13,790 38,417 11,538 49,955 10,660 8,629 19,289 8,287 27,577 9,524 37,101 FX Hedge Gain (19,904 ) (89,402 ) - - - - - - - - - - - - - - EBITDA 367,440 419,287 130,557 135,401 265,958 148,119 414,077 160,276 574,353 38,557 53,456 92,013 178,643 270,656 195,814 466,470 Contingent Consideration - 12,255 (37 ) 14 (22 ) 500 477 2,064 2,541 (366 ) (1,931 ) (2,297 ) (58 ) (2,355 ) (9,873 ) (12,228 ) Goodwill Impairment - - - - - - - - - - 92,416 92,416 - 92,416 - 92,416 Acquisition & Integration Expenses - 49,554 - - - - - 7,138 7,138 - - - - - - - Legal Contingency Costs - - - - - - - - - 115,000 - 115,000 - 115,000 - 115,000 COVID-19 Credits (6,486 ) - - - - - - - - - - - - - - - Adjusted EBITDA 360,954 481,096 130,520 135,415 265,936 148,619 414,554 169,478 584,032 153,191 143,941 297,132 178,585 475,717 185,941 661,658 9

the item shown at left

other guidance in this release

Text is the filed exhibit, verbatim.