EXHIBIT 99.1 Exhibit 99.1 NEWS RELEASE July 30, 2025 Tetra Tech Reports Strong Third Quarter 2025 Results · Revenue $1.37 billion and Net Revenue $1.15 billion · Net Revenue of $1.06 billion, up 11% Y/Y excluding USAID and DOS · Operating Income $165 million, up 28% Y/Y · EPS $0.43, up 34% Y/Y · Operating Cash Flow $350 million, up 148% 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 third quarter ended June 29, 2025. Q3 FY25 YTD FY25 $ million (except EPS data) Reported Excluding USAID / DOS Adjusted 1 Excluding USAID / DOS Revenue $ 1,370 $ 1,264 $ 4,112 $ 3,560 Net Revenue 1 $ 1,153 $ 1,062 $ 3,454 $ 2,990 Operating Income $ 165 $ 159 $ 432 $ 396 EPS $ 0.43 $ 0.41 $ 1.11 $ 1.01 Backlog $ 4,277 $ 4,149 $ 4,277 $ 4,149 Third Quarter Highlights (Excluding USAID and DOS) · Revenue increased 10% Y/Y to $1.26 billion · Net Revenue increased 11% Y/Y to $1.06 billion · Operating Income increased 37% Y/Y to $159 million · EPS increased 46% Y/Y to $0.41 · Backlog $4.15 billion, up Y/Y and sequentially · Days sales outstanding: 54 days Year to Date Highlights (Excluding USAID and DOS) · Revenue increased 10% Y/Y to $3.56 billion · Net Revenue increased 10% Y/Y to $2.99 billion · Adjusted Operating Income increased 24% Y/Y to $396 million · Adjusted EPS increased 31% Y/Y to $1.01 1 Non-GAAP financial measures which the Company believes provide valuable perspectives on its business results. The reported adjusted operating income and EPS exclude non-cash goodwill impairment related to USAID in Q2-25 and legal contingency in Q1-25. Refer to tables at the end of the release and Regulation G Information for reconciliations to the comparable GAAP metrics. Recent Key Wins · $990 million multiple-award contract for engineering design for NAVFAC Pacific · $249 million multiple-award contract for energy resilience for USACE Huntsville District · $248 million multiple-award contract for planning and engineering services for USACE Europe District · $190 million multiple-award contract for planning and engineering services for USACE Honolulu District · $94 million single-award contract for emergency preparedness and response services for U.S. EPA · $45 million multiple-award contract for environmental services for U.S. Department of the Interior · $22 million single-award contract for disaster recovery services for the State of Georgia · $10 million single-award contract for water digital automation systems for Los Angeles County Quarterly Dividend and Share Repurchase Program On July 28, 2025, Tetra Tech’s Board of Directors approved the Company’s 45 th consecutive quarterly dividend at an amount of $0.065 per share, a 12% increase year-over-year, payable on August 29, 2025, to stockholders of record as of August 15, 2025. In the third quarter, Tetra Tech repurchased $25 million of common stock. Additionally, as of June 29, 2025, the Company had $648 million remaining under the approved share repurchase programs. Chairman and CEO Comments Dan Batrack, Chairman and CEO, commented, “Tetra Tech delivered another strong quarter with increasing revenue, record operating income, and significant operating margin expansion over the third quarter of last year. This performance is being driven by our high-end water, environmental and sustainable infrastructure services, which includes our clients’ increased funding for preparing and responding to natural disasters. Although the financial results for fiscal 2025 to date have exceeded our initial expectations, we are continuing to navigate the near-term financial impacts from the changes in U.S. federal government priorities and the related secondary impacts to our end markets.” 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 2025, Tetra Tech expects net reven ue 2 to range from $4.454 billion to $4.554 billion and adjusted EPS 3 g uidance to range from $1.49 to $1.54. For the fourth quarter of fiscal 2025, Tetra Tech expects net revenue to range from $1.0 billion to $1.1 billion and EPS to range from $0.38 to $0.43. 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. 3 The adjustments in our guidance for EPS exclude legal contingency of $0.35 in Q1-25 and goodwill impairment of $0.31 in Q2-25. 2 Webcast Investors will have the opportunity to access a live audio-visual webcast and supplemental financial information concerning the third quarter of fiscal 2025 results through a link posted on the Company’s website at tetratech.com on July 31, 2025, at 8:00 a.m. (PT). Reconciliation of GAAP and Non-GAAP Items In thousands (except EPS data) Three Months Ended Nine Months Ended June 29, 2025 June 30, 2024 June 29, 2025 June 30, 2024 Revenue $ 1,369,816 $ 1,344,323 $ 4,112,490 $ 3,824,205 USAID / DOS (106,084 ) (194,753 ) (552,572 ) (577,762 ) Revenue excl. USAID / DOS $ 1,263,732 $ 1,149,570 $ 3,559,918 $ 3,246,443 Revenue $ 1,369,816 $ 1,344,323 $ 4,112,490 $ 3,824,205 Subcontractor costs (216,800 ) (234,742 ) (658,439 ) (646,828 ) Net revenue $ 1,153,016 $ 1,109,581 $ 3,454,051 $ 3,177,377 USAID / DOS (91,305 ) (154,503 ) (464,104 ) (470,294 ) Net revenue excl. USAID / DOS $ 1,061,711 $ 955,078 $ 2,989,947 $ 2,707,083 Operating Income $ 164,986 $ 128,630 $ 227,114 $ 357,395 Legal contingency - - 115,000 - Goodwill impairment - - 92,416 - Contingent consideration (58 ) 500 (2,355 ) 477 Adjusted Operating Income $ 164,928 $ 129,130 $ 432,175 $ 357,872 USAID / DOS (5,492 ) (12,918 ) (36,638 ) (39,434 ) Adjusted OI excl. USAID / DOS $ 159,436 $ 116,212 $ 395,537 $ 318,438 EPS $ 0.43 $ 0.32 $ 0.45 $ 0.88 Legal contingency - - 0.35 - Goodwill impairment - - 0.31 - Adjusted EPS $ 0.43 $ 0.32 $ 1.11 $ 0.88 USAID / DOS (0.02 ) (0.04 ) (0.10 ) (0.11 ) Adj. EPS excl. USAID / DOS $ 0.41 $ 0.28 $ 1.01 $ 0.77 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 30,000 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) As of June 29, September 29, 2025 2024 Assets Current assets: Cash and cash equivalents $ 242,833 $ 232,689 Accounts receivable, net 1,127,519 1,051,461 Contract assets 142,852 129,678 Prepaid expenses and other current assets 106,592 113,555 Total current assets 1,619,796 1,527,383 Property and equipment, net 70,302 73,065 Right-of-use assets, operating leases 186,145 177,950 Goodwill 2,084,872 2,046,569 Intangible assets, net 157,752 160,585 Deferred tax assets 109,477 105,529 Other non-current assets 125,103 101,595 Total assets $ 4,353,447 $ 4,192,676 Liabilities and Equity Current liabilities: Accounts payable $ 234,591 $ 197,440 Accrued compensation 313,335 332,096 Contract liabilities 389,856 351,738 Short-term lease liabilities, operating leases 64,109 63,419 Current contingent earn-out liabilities 35,362 26,934 Other current liabilities 338,868 247,900 Total current liabilities 1,376,121 1,219,527 Deferred tax liabilities 30,673 30,162 Long-term debt 862,483 812,634 Long-term lease liabilities, operating leases 145,045 140,095 Non-current contingent earn-out liabilities 34,369 21,812 Other non-current liabilities 162,660 138,033 Total liabilities 2,611,351 2,362,263 Equity: Preferred stock - authorized, 2,000 shares of $0.01 par value; no shares issued and outstanding at June 29, 2025 and September 29, 2024 - - Common stock - authorized, 750,000 shares of $0.01 par value; issued and outstanding, 262,752 and 267,717 shares at June 29, 2025 and September 29, 2024, respectively 2,628 2,677 Additional paid-in capital - 35,900 Accumulated other comprehensive loss (65,117 ) (78,875 ) Retained earnings 1,804,429 1,870,620 Tetra Tech stockholders' equity 1,741,940 1,830,322 Noncontrolling interests 156 91 Total stockholders' equity 1,742,096 1,830,413 Total liabilities and stockholders' equity $ 4,353,447 $ 4,192,676 6 Tetra Tech, Inc Consolidated Statements of Income (unaudited - in thousands, except per share data) Three Months Ended Nine Months Ended June 29, June 30, June 29, June 30, 2025 2024 2025 2024 Revenue $ 1,369,816 $ 1,344,323 $ 4,112,490 $ 3,824,205 Subcontractor costs (216,800 ) (234,742 ) (658,439 ) (646,828 ) Other costs of revenue (901,477 ) (886,409 ) (2,766,854 ) (2,556,212 ) Gross profit 251,539 223,172 687,197 621,165 Selling, general and administrative expenses (86,611 ) (94,042 ) (255,022 ) (263,293 ) Legal contingency costs - - (115,000 ) - Contingent consideration - fair value adjustments 58 (500 ) 2,355 (477 ) Impairment of goodwill - - (92,416 ) - Income from operations 164,986 128,630 227,114 357,395 Interest expense, net (8,288 ) (9,912 ) (23,996 ) (29,374 ) Income before income tax expense 156,698 118,718 203,118 328,021 Income tax expense (42,815 ) (32,894 ) (83,045 ) (90,758 ) Net income 113,883 85,824 120,073 237,263 Net income attributable to noncontrolling interests (39 ) (14 ) (94 ) (35 ) Net income attributable to Tetra Tech $ 113,844 $ 85,810 $ 119,979 $ 237,228 Earnings per share attributable to Tetra Tech: Basic $ 0.43 $ 0.32 $ 0.45 $ 0.89 Diluted $ 0.43 $ 0.32 $ 0.45 $ 0.88 Weighted-average common shares outstanding: Basic 263,026 267,575 265,589 267,255 Diluted 264,855 270,260 268,113 269,503 7 Tetra Tech, Inc. Consolidated Statements of Cash Flows (unaudited - in thousands) Nine Months Ended June 29, June 30, 2025 2024 Cash flows from operating activities: Net income $ 120,073 $ 237,263 Adjustments to reconcile net income to net cash provided by operating activities: Depreciation and amortization 43,636 56,718 Amortization of stock-based awards 25,789 23,713 Deferred income taxes (7,656 ) (9,736 ) Provision for losses on accounts receivables 3,406 - Impairment of goodwill 92,416 - Fair value adjustments to contingent consideration (2,355 ) 477 Gain on cash surrender value of life insurance policies (1,599 ) - Other non-cash items 3,781 3,769 Changes in operating assets and liabilities, net of effects of business acquisitions: Accounts receivable and contract assets (65,886 ) (54,286 ) Prepaid expenses and other assets (21,720 ) (18,437 ) Accounts payable 27,539 18,991 Accrued compensation (15,991 ) (7,982 ) Contract liabilities 44,486 33,011 Income taxes receivable/payable 32,818 (16,436 ) Cash settled contingent earn-out liability (7,420 ) - Other liabilities 85,521 (13,955 ) Net cash provided by operating activities 356,838 253,110 Cash flows from investing activities: Payments for business acquisitions, net of cash acquired (97,693 ) (93,650 ) Capital expenditures (13,396 ) (11,324 ) Proceeds from sale of assets 882 666 Proceeds from company-owned life insurance policies 1,934 - Net cash used in investing activities (108,273 ) (104,308 ) Cash flows from financing activities: Proceeds from borrowings 715,000 180,000 Repayments on long-term debt (665,000 ) (200,000 ) Payment of debt issuance costs (2,738 ) - Repurchases of common stock (199,984 ) - Shares repurchased for tax withholdings on share-based awards (13,942 ) (12,906 ) Payments of contingent earn-out liabilities (14,805 ) (29,112 ) Stock options exercised 216 2,690 Dividends paid (47,992 ) (43,303 ) Principal payments on finance leases (5,742 ) (4,827 ) Net cash used in financing activities (234,987 ) (107,458 ) Effect of exchange rate changes on cash and cash equivalents (3,434 ) 2,146 Net increase in cash and cash equivalents 10,144 43,490 Cash and cash equivalents at beginning of period 232,689 168,831 Cash and cash equivalents at end of period $ 242,833 $ 212,321 Supplemental information: Cash paid during the period for: Interest $ 23,837 $ 26,867 Income taxes, net of refunds received of $13.6 million and $4.0 million $ 55,523 $ 115,933 Noncash financing activities: Excise taxes accrued but not paid $ 1,513 $ - 8 Tetra Tech, Inc. Regulation G Information June 29, 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 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 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 ) 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 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 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 ) 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 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 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 ) 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 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 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 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 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 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 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 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 Contingent Consideration - 12,255 (37 ) 14 (22 ) 500 477 2,064 2,541 (366 ) (1,931 ) (2,297 ) (58 ) (2,355 ) Goodwill Impairment - - - - - - - - - - 92,416 92,416 - 92,416 Acquisition & Integration Expenses - 49,554 - - - - - 7,138 7,138 - - - - - Legal Contingency Costs - - - - - - - - - 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 9

the item shown at left

other guidance in this release

Text is the filed exhibit, verbatim.