Osisko Development Corp. — Declaration of Voting Results & Voting Rights Announcements 2024

May 8, 2024

OSISKO DEVELOPMENT CORP.

Report of Voting Results Pursuant to Section 11.3 of

National Instrument 51-102 – Continuous Disclosure Obligations

In respect of the annual meeting of holders of common shares of Osisko Development Corp. (the “ Company ”) held on May 7, 2024 (the “ Meeting ”), the following sets forth a brief description of each matter that was voted upon at the Meeting and the outcome of the vote. A detailed description of the business of the Meeting is contained in the Company’s management information circular dated March 18, 2024 (the “ Circular ”), which is available under the Company’s profile on SEDAR+ at www.sedarplus.ca.

1. Election of Directors

According to votes received by the scrutineer, the Chair of the Meeting declared that each of the six director nominees proposed by management were elected. The voting results were as follows:

Nominee	Votes For	% of VotesFor	Votes Against	% of VotesAgainst
Sean Roosen	49,372,453	95.75%	2,148,533	4.25%
Charles E. Page	49,300,002	97.58%	1,220,984	2.42%
Marina Katusa	49,320,043	97.62%	1,200,943	2.38%
Michele McCarthy	49,289,021	97.56%	1,231,965	2.44%
Duncan Middlemiss	49,194,382	97.37%	1,326,604	2.63%
David Danziger	49,371,868	97.73%	1,149,118	2.28%

2. Appointment of Auditors

According to votes received by the scrutineer, the Chair of the Meeting declared that the shareholders approved the appointment of PricewaterhouseCoopers LLP/s.r.l./s.e.n.c.r.l. to serve as the auditor of the Company for 2024 and at a remuneration to be fixed by the board of directors. The voting results were as follows:

Votes For	% of Votes For	Votes Withheld	% of Votes Withheld
53,571,208	99.74%	145,321	0.26%

3. Amended Stock Option Plan

According to votes received by the scrutineer, the Chair of the Meeting declared that the shareholders adopted the resolution (the full text of which is reproduced in the Circular) to confirm and approve the Company’s amended stock option plan. The voting results were as follows:

Votes For	% of Votes For	Votes Against	% of Votes Against
47,878,481	94.77%	2,642,505	5.23%

4. Amended Deferred Share Unit Plan

According to votes received by the scrutineer, the Chair of the Meeting declared that the shareholders adopted the resolution (the full text of which is reproduced in the Circular) to confirm and approve the Company’s

amended deferred share unit plan. The voting results were as follows:

Votes For	% of Votes For	Votes Against	% of Votes Against
47,913,763	94.84%	2,607,224	5.16%

Dated at Montreal, Quebec this 7[th] day of May, 2024.