EXHIBIT 99.1 Exhibit 99.1 NEWS RELEASE April 29, 2026 Tetra Tech Reports Strong Second Quarter 2026 Results and Raises Fiscal Year 2026 Guidance · Revenue $1.22 billion; Net Revenue $1.05 billion · Operating Income $132 million; EBITDA $146 million · EPS $0.36; Adjusted EPS $0.34 · Backlog $4.28 billion, up 8% sequentially · Raising FY26 Net Revenue and EPS guidance 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 second quarter ended March 29, 2026. Revenue and revenue, net of subcontractor costs (net revenue) 1 , in the second quarter totaled $1.22 billion and $1.05 billion, respectively . Net revenue increased 8% Y/Y excluding USAID / DOS and disasters. Operating income was $132 million and EBITDA 1 was $146 million; EBITDA margin was up 90 basis points Y/Y. EPS was $0.36 and adjusted EPS 1 was $0.34. Backlog was $4.28 billion at the end of the second quarter, up 8% sequentially. Cash from operations was $165 million in the second quarter and $688 million over the trailing twelve months, resulting in a DSO of 58 days. Recent Key Wins · $400 million multiple-award contract for consulting and engineering services for USACE Huntsville District · $100 million multiple-award contract for environmental services for U.S. Air Force · $99 million single-award contract for engineering and technical consulting services for U.S. Navy · $49 million multiple-award contract for engineering and technical consulting services for USACE Portland District · £18 million single-award contract for consulting services for Northern Ireland Water · $14 million task order contract for technology consulting services for Defense Logistics Agency · Netherlands Water framework contracts for engineering and technical consulting services · Port of Los Angeles master services agreement for environmental engineering services · United Utilities contract for WaterNet™ SaaS water network management solution services 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. Executive Management Comments Roger Argus, Chief Executive Officer, commented, “We delivered a strong second quarter, driven by growth across our end markets in water, environment, and sustainable infrastructure. In U.S. federal, we saw increased orders from defense agencies related to new facilities and infrastructure modernization. Our high-end consulting services for providing water supplies and mitigating environmental impacts are increasingly critical to gaining community support for the establishment of data centers. Our international operations grew due to demand for front-end water and infrastructure consulting services. These positive trends led to backlog growth and improved revenue visibility for the remainder of the year, leading to our increased guidance for fiscal 2026.” Steve Burdick, Chief Financial Officer, stated, “Tetra Tech has started off the first half of fiscal 2026 with the strongest cash flow generation on record with $238 million from operations. These exceptional cash flows have consequently provided better returns for shareholders through our stock buyback program, which has returned $100 million so far this year, and our cash dividend program. Our ability to consistently generate cash in excess of net income has allowed the Company to once again increase our quarterly cash dividends by an additional 11% over last year. Cash generated over the last twelve months of $688 million has allowed us to fund acquisitions, complete stock buybacks, and pay dividends, while deleveraging our net debt by more than 25% from this time last year.” Quarterly Dividend and Share Repurchase Program On April 27, 2026, Tetra Tech’s Board of Directors approved a quarterly dividend in the amount of $0.072 per share, an 11% increase year-over-year, payable on June 2, 2026, to stockholders of record as of May 14, 2026. This is the 44 th consecutive double-digit increase in the Company’s quarterly dividend. In the second quarter of fiscal 2026, Tetra Tech repurchased $50 million of common stock. Additionally, as of March 29, 2026, the Company had $498 million remaining under its share repurchase program. Six-Month Results Revenue for the six-month period was $2.43 billion and net revenue was $2.09 billion. Net revenue increased 8% Y/Y excluding USAID / DOS and disasters. Operating income was $273 million, EPS was $0.76, and cash flow from operations was $238 million. 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 is increasing the full year guidance for net revenue 2 to range from $4.25 billion to $4.40 billion and adjusted EPS 3 to range from $1.50 to $1.58. For the third quarter of fiscal 2026, Tetra Tech expects net revenue to range from $1.05 billion to $1.10 billion and EPS to range from $0.38 to $0.41. 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 only adjustments in our guidance for EPS are to exclude the gain on business disposition and contingent consideration in the first six months of fiscal 2026. Webcast Investors will have the opportunity to access a live audio-visual webcast and supplemental financial information concerning the second quarter of fiscal 2026 results through a link posted on the Company’s website at tetratech.com on April 30, 2026, at 8:00 a.m. (PT). Reconciliation of GAAP and Non-GAAP Items In thousands (except EPS data) Three Months Ended Six Months Ended March 29, 2026 March 30, 2025 March 29, 2026 March 30, 2025 Revenue $ 1,220,157 $ 1,322,113 $ 2,430,820 $ 2,742,674 Subcontractor costs (170,524 ) (218,408 ) (344,011 ) (441,639 ) Net revenue $ 1,049,633 $ 1,103,705 $ 2,086,809 $ 2,301,035 Operating Income $ 131,523 $ 39,603 $ 272,517 $ 62,129 Contingent consideration (58 ) (1,931 ) (7,506 ) (2,297 ) Legal contingency - - - 115,000 Goodwill impairment - 92,416 - 92,416 Adjusted Operating Income $ 131,465 $ 130,088 $ 265,011 $ 267,248 EPS $ 0.36 $ 0.02 $ 0.76 $ 0.02 Contingent consideration - - (0.02 ) - Legal contingency - - - 0.35 Goodwill impairment - 0.31 - 0.31 Gain on divestiture (0.02 ) - (0.05 ) - Adjusted EPS $ 0.34 $ 0.33 $ 0.69 $ 0.68 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 28, 2025. 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. 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. Tetra Tech, Inc. Balance Sheet (unaudited - in thousands, except par value) March 29, September 28, 2026 2025 Assets Current assets: Cash and cash equivalents $ 223,612 $ 167,459 Accounts receivable, net 1,047,330 1,158,928 Contract assets 146,455 138,232 Prepaid expenses and other current assets 124,622 98,768 Assets held-for-sale - 57,502 Total current assets 1,542,019 1,620,889 Property and equipment, net 65,367 66,148 Right-of-use assets, operating leases 206,527 197,618 Goodwill 2,209,588 2,049,874 Intangible assets, net 129,285 121,160 Deferred tax assets 78,763 106,238 Other non-current assets 130,682 120,247 Total assets $ 4,362,231 $ 4,282,174 Liabilities and Equity Current liabilities: Accounts payable $ 204,792 $ 204,725 Accrued compensation 245,645 346,912 Contract liabilities 410,858 420,254 Short-term lease liabilities, operating leases 73,743 69,099 Current contingent earn-out liabilities 44,449 24,826 Liabilities held-for-sale - 25,115 Other current liabilities 249,244 288,113 Total current liabilities 1,228,731 1,379,044 Deferred tax liabilities 20,022 21,333 Long-term debt 880,162 763,363 Long-term lease liabilities, operating leases 155,825 154,695 Non-current contingent earn-out liabilities 63,882 32,135 Other non-current liabilities 149,860 151,440 Total liabilities 2,498,482 2,502,010 Equity: Preferred stock - authorized, 2,000 shares of $0.01 par value; no shares issued and outstanding at March 29, 2026 and September 28, 2025 - - Common stock - authorized, 750,000 shares of $0.01 par value; issued and outstanding, 259,525 and 261,418 shares at March 29, 2026 and September 28, 2025, respectively 2,595 2,614 Accumulated other comprehensive loss (94,684 ) (95,777 ) Retained earnings 1,955,468 1,872,948 Tetra Tech stockholders' equity 1,863,379 1,779,785 Noncontrolling interests 370 379 Total stockholders' equity 1,863,749 1,780,164 Total liabilities and stockholders' equity $ 4,362,231 $ 4,282,174 Tetra Tech, Inc. Consolidated Statements of Income (unaudited - in thousands, except per share data) Three Months Ended Six Months Ended March 29, March 30, March 29, March 30, 2026 2025 2026 2025 Revenue $ 1,220,157 $ 1,322,113 $ 2,430,820 $ 2,742,674 Subcontractor costs (170,524 ) (218,408 ) (344,011 ) (441,639 ) Other costs of revenue (835,542 ) (889,523 ) (1,652,347 ) (1,865,376 ) Gross profit 214,091 214,182 434,462 435,659 Selling, general and administrative expenses (82,626 ) (84,094 ) (169,451 ) (168,411 ) Legal contingency costs - - - (115,000 ) Contingent consideration - fair value adjustments 58 1,931 7,506 2,297 Impairment of goodwill - (92,416 ) - (92,416 ) Income from operations 131,523 39,603 272,517 62,129 Interest expense, net (8,838 ) (8,491 ) (15,966 ) (15,709 ) Other non-operating income 4,651 - 12,361 - Income before income tax expense 127,336 31,112 268,912 46,420 Income tax expense (33,538 ) (25,700 ) (69,892 ) (40,230 ) Net income 93,798 5,412 199,020 6,190 Net income attributable to noncontrolling interests (175 ) (24 ) (369 ) (55 ) Net income attributable to Tetra Tech $ 93,623 $ 5,388 $ 198,651 $ 6,135 Earnings per share attributable to Tetra Tech: Basic $ 0.36 $ 0.02 $ 0.76 $ 0.02 Diluted $ 0.36 $ 0.02 $ 0.76 $ 0.02 Weighted-average common shares outstanding: Basic 260,144 265,728 260,635 266,819 Diluted 261,919 267,439 262,483 269,691 Tetra Tech, Inc. Consolidated Statements of Cash Flows (unaudited, in thousands) Six Months Ended March 29, March 30, 2026 2025 Cash flows from operating activities: Net income $ 199,020 $ 6,190 Adjustments to reconcile net income to net cash provided by operating activities: Depreciation and amortization 28,337 29,939 Amortization of stock-based awards 17,670 17,027 Deferred income taxes 27,069 (6,164 ) Provision for losses on accounts receivables - 3,331 Gain on sale of divested business (12,361 ) - Impairment of goodwill - 92,416 Fair value adjustments to contingent consideration (7,506 ) (2,297 ) Gain on cash surrender value of life insurance policies - (1,599 ) Other non-cash items 2,387 4,267 Changes in operating assets and liabilities, net of effects of business acquisitions and divestitures: Accounts receivable and contract assets 143,255 (203,055 ) Prepaid expenses and other assets 1,371 (28,322 ) Accounts payable (8,236 ) 66,917 Accrued compensation (106,848 ) (83,088 ) Contract liabilities (9,539 ) 37,354 Income taxes receivable/payable (14,047 ) (3,253 ) Cash settled on contingent earn-out liability - (7,420 ) Other liabilities (22,961 ) 84,997 Net cash provided by operating activities 237,611 7,240 Cash flows from investing activities: Payments for business acquisitions, net of cash acquired (175,000 ) (5,680 ) Capital expenditures (10,144 ) (9,022 ) Proceeds from divested business, net 40,263 - Proceeds from company-owned life insurance policies - 1,934 Net cash used in investing activities (144,881 ) (12,768 ) Cash flows from financing activities: Proceeds from borrowings 240,000 215,000 Repayments on long-term debt (125,000 ) (15,000 ) Repurchases of common stock (102,010 ) (174,984 ) Shares repurchased for tax withholdings on share-based awards (12,430 ) (13,848 ) Payments of contingent earn-out liabilities (2,842 ) (14,445 ) Stock options exercised 458 171 Dividends paid (33,852 ) (30,900 ) Principal payments on finance leases (3,841 ) (3,431 ) Net cash used in financing activities (39,517 ) (37,437 ) Effect of exchange rate changes on cash and cash equivalents 2,027 (10,291 ) Net increase (decrease) in cash and cash equivalents 55,240 (53,256 ) Cash and cash equivalents at beginning of period 168,372 232,689 Cash and cash equivalents at end of period $ 223,612 $ 179,433 Tetra Tech, Inc. Regulation G Information March 29, 2026 Reconciliation of Revenue to Revenue, Net of Subcontractor Costs ("Net Revenue") (in millions) 2025 2026 2023 2024 1st Qtr 2nd Qtr 6 Mos 3rd Qtr 9 Mos 4th Qtr Total 1st Qtr 2nd Qtr 6 Mos Consolidated Revenue 4,522.6 5,198.7 1,420.6 1,322.1 2,742.7 1,369.8 4,112.5 1,330.1 5,442.6 1,210.7 1,220.2 2,430.8 Subcontractor Costs (771.5 ) (876.8 ) (223.3 ) (218.4 ) (441.7 ) (216.8 ) (658.5 ) (166.8 ) (825.3 ) (173.5 ) (170.5 ) (344.0 ) Net Revenue 3,751.1 4,321.9 1,197.3 1,103.7 2,301.0 1,153.0 3,454.0 1,163.3 4,617.3 1,037.2 1,049.7 2,086.8 GSG Segment Revenue 2,300.7 2,624.2 791.4 698.9 1,490.2 709.4 2,199.6 628.9 2,828.6 525.5 559.4 1,084.9 Subcontractor Costs (484.3 ) (540.5 ) (144.0 ) (134.6 ) (278.5 ) (136.8 ) (415.3 ) (88.4 ) (503.7 ) (93.4 ) (100.9 ) (194.3 ) Net Revenue 1,816.4 2,083.7 647.4 564.3 1,211.7 572.6 1,784.3 540.5 2,324.9 432.1 458.5 890.6 CIG Segment Revenue 2,292.7 2,634.4 644.9 637.8 1,282.6 676.6 1,959.1 721.2 2,680.2 704.2 676.2 1,380.3 Subcontractor Costs (358.0 ) (396.2 ) (94.9 ) (98.3 ) (193.2 ) (96.1 ) (289.4 ) (98.3 ) (387.7 ) (99.1 ) (85.0 ) (184.1 ) Net Revenue 1,934.7 2,238.2 550.0 539.5 1,089.4 580.5 1,669.7 622.9 2,292.5 605.1 591.2 1,196.2 Reconciliation of Net Income Attributable to Tetra Tech to Adjusted EBITDA (in thousands) 2025 2026 2023 2024 1st Qtr 2nd Qtr 6 Mos 3rd Qtr 9 Mos 4th Qtr Total 1st Qtr 2nd Qtr 6 Mos Net Income Attributable to Tetra Tech 273,420 333,382 747 5,388 6,135 113,844 119,979 127,745 247,724 105,028 93,623 198,651 Income Tax Expense 127,526 130,023 14,530 25,700 40,230 42,815 83,045 46,624 129,668 36,354 33,538 69,892 Interest Expense 1 46,537 37,271 7,218 8,491 15,709 8,287 23,996 6,806 30,802 7,128 8,838 15,966 Depreciation 19,980 23,722 5,402 5,248 10,650 5,410 16,059 5,115 21,175 5,608 5,550 11,159 Amortization 41,226 49,955 10,660 8,629 19,289 8,287 27,577 9,524 37,101 8,387 8,791 17,178 FX Hedge Gain (89,402 ) - - - - - - - - - - - Gain on sale of divested business - - - - - - - - - (7,710 ) (4,651 ) (12,361 ) EBITDA 419,287 574,353 38,557 53,456 92,013 178,643 270,656 195,814 466,470 154,795 145,689 300,485 Contingent Consideration 12,255 2,541 (366 ) (1,931 ) (2,297 ) (58 ) (2,355 ) (9,873 ) (12,228 ) (7,447 ) (58 ) (7,506 ) Goodwill Impairment - - - 92,416 92,416 - 92,416 - 92,416 - - - Acquisition & Integration Expenses 2 49,554 7,138 - - - - - - - - - - Legal Contingency Costs - - 115,000 - 115,000 - 115,000 - 115,000 - - - Adjusted EBITDA 481,096 584,032 153,191 143,941 297,132 178,585 475,717 185,941 661,658 147,348 145,631 292,979 1 Includes write-off of deferred debt origination fees of $3.8M in fiscal 2023 2 Includes lease impairment charge of $16.4M in fiscal 2023

the item shown at left

other guidance in this release

Text is the filed exhibit, verbatim.