Osisko Development to Complete Fourth Deferred Payment Installment in Connection with the Tintic Acquisition

Osisko Development Corp. (NYSE: ODV, TSXV: ODV) ("Osisko Development" or the "Company") announces that, in accordance with the terms of the Company's previously-completed acquisition in May 2022 of a 100% ownership interest in the Tintic Project, located in Utah, U.S.A., (the "Tintic Acquisition"), the Company intends to satisfy the fourth of five deferred payments (the "Fourth Deferred Payment") to certain sellers of the Tintic Project (the "Sellers") in common shares of the Company ("Common Shares").

The Fourth Deferred Payment of US$2,500,000 (or C$3,453,000 based on a USD/CAD exchange rate of 1.3812) is expected to be paid entirely in Common Shares at a deemed price of approximately C$3.9613 per Common Share (based on the 20-day VWAP as of the closing of the market on May 26, 2026), resulting in the issuance of 871,683 Common Shares to the Sellers in full satisfaction of the Fourth Deferred Payment.

The issuance of the Common Shares in satisfaction of the Fourth Deferred Payment remains subject to the approval of the TSX Venture Exchange (the "Exchange").

For additional details regarding the Tintic Acquisition, please refer to the Company's news releases dated January 25, 2022 (entitled "Osisko Development Announces Proposed Acquisition of Tintic Consolidated Metals") and May 30, 2022 (entitled "Osisko Development Completes Acquisition of Tintic Consolidated Metals, Finalizes Binding Stream Terms and Satisfies Escrow Release Condition For Brokered Subscription Receipt Financing").

ABOUT OSISKO DEVELOPMENT CORP.

Osisko Development Corp. is a continental North American gold development company focused on past producing mining camps with district-scale potential. The Company's objective is to become an intermediate gold producer through the development of its flagship, fully permitted, 100%-owned Cariboo Gold Project, located in central British Columbia, Canada. Its project pipeline is complemented by the Tintic Project located in the historic East Tintic mining district in Utah, U.S.A., a brownfield property with significant exploration potential, extensive historical mining data, and access to established infrastructure. Osisko Development is focused on developing long-life mining assets in mining-friendly jurisdictions while maintaining a disciplined approach to capital allocation, development risk management, and mineral inventory growth.

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CAUTION REGARDING FORWARD-LOOKING STATEMENTS

This news release contains "forward-looking information" (within the meaning of applicable Canadian securities laws) and "forward-looking statements" (within the meaning of the U.S. Private Securities Litigation Reform Act of 1995, as amended) (collectively, "forward-looking statements"). Such forward-looking statements are identified with words such as "may", "will", "would", "could", "anticipate", "believe", "expect", "plan", "intend", "potential", "estimate", "propose", "project", "outlook", "foresee", "objective", "strategy", variants of these words or the negative or comparable terminology, as well as terms usually used in the future and the conditional. Information contained in forward-looking statements is based upon certain material assumptions that were applied in drawing a conclusion or making a forecast or projection, including the assumptions, qualifications, limitations or statements pertaining to: the ability and timing of the Company to complete the Fourth Deferred Payment; to obtain the Exchange's final approval of the issuance of the Common Shares in satisfaction of the Fourth Deferred Payment; to obtain the Exchange's final approval of the Agreement; the ability to develop the Cariboo Gold Project and its status as being fully permitted; the exploration potential and prospectivity (if any) of its properties. Such forward-looking statements are based on a number of risks, uncertainties and assumptions which may cause actual results or other expectations to differ materially from those anticipated and which may prove to be incorrect. These assumptions include, but are not limited to: the absence of further work stoppages or suspensions at the Project; favourable regulatory conditions and approvals; the ability to maintain adequate personnel and contractor levels; the absence of unforeseen ground conditions or other geological challenges; the availability of necessary equipment, supplies and infrastructure; and general economic and market conditions. Actual results could differ materially due to a number of factors, including, without limitation: risks related to the exploration, development and operation of the Cariboo Gold Project; health, safety and security incidents; regulatory delays or changes in regulatory framework and applicable laws; labour shortages or disputes; general economic and market conditions and business conditions in the mining industry; fluctuations in commodity and currency exchange rates; changes in regulatory framework and applicable laws, as well as those risks and factors disclosed in the Company's most recent annual information form, financial statements and management's discussion and analysis as well as other public filings on SEDAR+ (www.sedarplus.ca) and on EDGAR (www.sec.gov). Although the Company believes the expectations conveyed by the forward-looking statements are reasonable based on information available as of the date hereof, no assurances can be given as to future results, levels of activity and achievements. The Company disclaims any obligation to update any forward-looking statements, whether as a result of new information, future events or results or otherwise, except as required by law. Forward-looking statements are not guarantees of performance and there can be no assurance that these forward-looking statements will prove to be accurate, as actual results and future events could differ materially from those anticipated in such statements. Accordingly, readers should not place undue reliance on forward-looking statements.

Neither the TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this news release. No stock exchange, securities commission or other regulatory authority has approved or disapproved the information contained herein.