Osisko Development Announces Inclusion in the GDXJ

Osisko Development Corp. (NYSE: ODV, TSXV: ODV,OTC:OSDVF) ("Osisko Development" or the "Company") is pleased to announce its inclusion in the VanEck Junior Gold Miners ETF ("GDXJ") pursuant to the GDXJ's semi-annual review and rebalancing announced on March 13, 2026, effective at the close of markets on March 20, 2026.

"We are very pleased to be included in the widely followed GDXJ index, which we believe will further elevate our market visibility and trading liquidity profile while broadening access to investors seeking exposure to the gold sector," stated Sean Roosen, Chairman and CEO. "This inclusion reflects the significant progress and milestones our team has achieved to date as we continue advancing and de-risking our flagship Cariboo Gold Project."

The GDXJ is a widely recognized exchange-traded fund designed to track the performance of the most liquid small- and mid-capitalization companies in the global gold and silver mining industries. For more information on the GDXJ, please visit: https://www.vaneck.com/us/en/investments/junior-gold-miners-etf-gdxj.

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 Company's inclusion in the GDXJ becoming effective at the close of markets on March 20, 2026 (if at all); the anticipated benefits (if any) of the inclusion in the GDXJ resulting in enhanced market visibility, trading liquidity and broader investor access; the inclusion being an indicator of progress or milestones achieved to date; continued advancement and de-risking of the Cariboo Gold Project (if at all); the duration of the Company's inclusion in the GDXJ; any future potential rebalances and levels of exposure over which the Company has no discretion over and any impacts to trading volumes as a result thereof; 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.