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Osisko Development Receives Environmental Assessment Certificate FOR Cariboo GOLD Project

Permits & Approvals

NYSE | TSXV : ODV NEWS RELEASE

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OSISKO DEVELOPMENT RECEIVES ENVIRONMENTAL ASSESSMENT CERTIFICATE

FOR CARIBOO GOLD PROJECT

Montréal, Québec, October 10, 2023 – Osisko Development Corp. (NYSE: ODV, TSXV: ODV) ("Osisko

Development" or the "Company") is pleased to announce that it has received an Environmental

Assessment ("EA") Certificate for the Company 's 100%-owned Cariboo Gold Project ( "Cariboo" or the

"Project") located in central British Columbia ("BC"), Canada.

The EA Certificate was granted by the Environmental Assessment Office of the Province of British Columbia

("EAO") and is supported by approval decision s from The Honourable George Heyman, Minister of

Environment and Climate Change Strategy and The Honourable Josie Osbourne, Minister of Energy, Mines

and Low Carbon Innovation . Receipt of the EA Certificate successfully concludes the EA process for the

Project, which was launched in October 2019 (see Figure 1).

Sean Roosen, Chairman and CEO, commented, "We are proud to be the first project, mining or

otherwise, in BC to receive an EA Certificate under the new streamlined EA framework of the Environmental

Assessment Act, 2018, and we commend the EAO and the Government of BC for establishing this robust

regulatory framework. Receipt of the EA certificate marks a major, positive milestone for the Cariboo Gold

Project. We continue to be encouraged by the steady progress made to de-risk the Project, bringing it closer

to shovel ready status. As we all know, development projects fall into two buckets – those with permits and

those without permits – and we are keen to unlock significant value at the Cariboo Gold Project as we move

along that path. I would like to thank our team for their dedication and tireless efforts in shepherding the

Project through this rigorous EA process that started in 2019. Together with our partners and stakeholders,

we remain committed to developing a modern, safe and sustainable operation that benefits all."

Lhtako Dené Nation Chief and Council remarked, "We are extremely proud of the relationship fostered

with Osisko Development on the Cariboo Gold Project over the past several years. This relationship has

been reciprocal from day one, and Lhtako Chief and Council look forward to many more years of partnership

and collaboration. Recently, Lhtako and Osisko engaged in the EA process for the Company's Cariboo

Gold Project. Environmental risks, as well as wildlife concerns, are top priorities for both Osisko

Development and the Lhtako Dené Nation. With the EA process now complete, we are quite confident that

all of our areas of concern have been addressed and mitigated throughout this process."

Chief Willie Sellars of the Williams Lake First Nation ( "WLFN") noted, "This decision reflects the

importance of meaningful collaboration between industry and Indigenous communities. This is a significant

milestone in advancing sustainable mining practices within our traditional territory, particularly the QR Mill

Site near Likely, BC. WLFN remains committed to monitoring the Project's progress to ensure it upholds

the highest environmental and cultural standards. We look forward to continuing our positive partnership

with Osisko Development."

Chief Rhonda Phillips of the Xatśūll First Nation added, "Xatśūll First Nation would like to congratulate

the success of Osisko Development in being awarded approva l for the Cariboo Gold Mine Project. We

acknowledge the hard work, dedication and collaboration that went into getting the Project to this point.

Working together to ensure resource development projects meet environmental sustainability targets and

improve the socio-economic wellbeing of our communities is a high priority for Xatśūll First Nation. We look

forward to continuing work with Osisko and other stakeholders to advance this Project."

The EA Certificate is the first step in the permitting process of the Cariboo Gold Project. As previously

disclosed on May 8, 2023, the Company announced the signing of two landmark permitting agreements –

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the Process Charter and the Joint Information Requirements Table – which establish a defined regulatory

process timeline and outline all agreed upon information requirements to support a robust permit application

for submission.

A Joint Permit Application for the BC Mines Act / Environmental Management Act is in process. The

Company anticipates receiving the permits in Q1 2024.

Figure 1: Cariboo Gold Project – Permitting Timeline Summary

Cariboo Gold Project

The Cariboo Gold Project is an advanced stage gold project 100% -owned by the Company located in the

historic Wells -Barkerville mining camp, in the District of Wells, central BC, Canada, that extends for

approximately 77 kilometres from northwest to southeast. The Company 's total land package consists of

415 mineral titles and covers an area of approximately 1,920 km2. As of December 30, 2022, the Project's

probable reserves totalled 16.70 million tonnes ("Mt") grading 3.78 g/t gold for 2.031 million ounces ("Moz"),

measured resources totalled 0.05 Mt grading 5.06 g/t gold for 0.008 Moz, indicated resources totalled 14.64

Mt grading 3.32 g/t gold for 1.564 Moz, and inferred resources totalled 15.47 Mt grading 3.44 g/t gold for

1.712 Moz.

The Company completed a Feasibility Study in January 2023 supported by the technical report titled

"Feasibility Study for the Cariboo Gold Project, District of Well, British Columbia, Canada ", dated January

10, 2023 (amended January 12, 2023) with an effective date of December 30, 2022) ("Cariboo Technical

Report"). Reference should be made to the full text of the Cariboo Technical Report, which was prepared

in accordance with National Instrument 43-101 – Standards of Disclosure for Mineral Projects ("NI 43-101")

and is available electronically on SEDAR+ ( www.sedarplus.ca) and on EDGAR ( www.sec.gov) under

Osisko Development's issuer profile.

For further information on the Cariboo Gold Project, please visit the Osisko Development corporate website

at www.osiskodev.com and the Cariboo project website at www.cariboogold.com.

Qualified Persons

The scientific and technical information in this news release has been reviewed and approved by François

Vézina, ing., P.Eng., MBA, Senior Vice President, Project Development, Technical Services and

Environment, who is a "qualified person" within the meaning of NI 43-101.

NYSE: ODV | TSXV: ODV

www.osiskodev.com 1

CARIBOO PROJECT PERMITTING TIMELINE

Significant progress made in de-risking the project through the permitting process

ENVIRONMENTAL ASSESSMENT

Early Engagement

Detailed Project Description

EA Readiness Decision

Process Planning

Application Development and Review

EAO* Review of Revised Application

Effects Assessment

Recommendation & Decision

PERMIT APPLICATION

Mine Review Committee (MRC) Screening

MRC Review

Drafting of initial reports, permits, conditions

Review of draft materials by MRC and ODV

Finalization of reports, permits, conditions

H1 H2

2020 2021

H1 H2

2022

Q1 Q2 Q3 Q4

2023

Q1 Q2 Q3 Q4 Q1

2024

Submission of Detailed Project Description

✓

✓

✓

✓

ODV Joint Application Submission

Decision

APPLICATION REFERRAL*Environmental Assessment Office (EAO)

Revised Application Submission✓

✓

✓

EA Certificate

Referral

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About Osisko Development Corp.

Osisko Development Corp. is a premier North American gold development company focused on high-quality

past-producing properties located in mining friendly jurisdictions with district scale potential. The Company's

objective is to become an intermediate gold producer by advancing its 100%-owned Cariboo Gold Project,

located in central B.C., Canada, the Tintic Project in the historic East Tintic mining district in Utah, U.S.A.,

and the San Antonio Gold Project i n Sonora, Mexico. In addition to considerable brownfield exploration

potential of these properties, that benefit from significant historical mining data, existing infrastructure and

access to skilled labour, the Company's project pipeline is complemented by other prospective exploration

properties. The Company 's strategy is to develop attractive, long -life, socially and environmentally

sustainable mining assets, while minimizing exposure to development risk and growing mineral resources.

For further information, please contact Osisko Development Corp.:

Sean Roosen Philip Rabenok

Chairman and CEO Director, Investor Relations

Email: [email protected] Email: [email protected]

Tel: +1 (514) 940-0685 Tel: +1 (437) 423-3644

CAUTION REGARDING FORWARD LOOKING STATEMENTS

Certain statements contained in this news release may be deemed "forward-looking statements" within the meaning of the United

States Private Securities Litigation Reform Act of 1995 and "forward-looking information" within the meaning of applicable Canadian

securities legislation. These forward‐looking statements, by their nature, require Osisko Development to make certain assumptions

and necessarily involve known and unknown risks and uncertainties that could cause actual results to differ materially from those

expressed or implied in these forward ‐looking statements. Forward ‐looking statements are not guarantees of performance. Words

such as "may", "will", "would", "could", "expect", "believe", "plan", "anticipate", "intend", "estimate", "continue", or the negative or

comparable terminology, as well as terms usually used in the future and the conditional, are intended to identify forward ‐looking

statements. Information contained in forward ‐looking statements is based upon certain material assumptions tha t were applied in

drawing a conclusion or making a forecast or projection, including the assumptions, qualifications and limitations relating to the

expected permitting timeline and summary (if at all); the ability of the Project to receive permit; the val ue that would be created

assuming the Project were to receive permits; positive future relationships with Lhtako Dené Nation, Xatśūll First Nation and Williams

Lake First Nation; the framework for regulatory process and timeline being adhered to; the results in the Cariboo Technical Report;

the capital resources available to Osisko Development; the ability of the Company to execute its planned activities, includin g as a

result of its ability to seek additional funding or to reduce planned expenditures; the ability of the Company to obtain future financing

and the terms of such financing; management's perceptions of historical trends, current conditions and expected future

developments; the utility and significance of historic data, including the significance of the district hosting past producing mines;

future mining activities; the timing and status of permitting; the results (if any) of further exploration work to define and expand mineral

resources; the ability of exploration work (including drilling) to accurately predict mineralization; the ability to generate additional drill

targets; the ability of management to understand the geology and potential of the Company's properties; the ability of the Company

to expand mineral resources beyond current mineral resource estimates; the ability of the Company to complete its exploration

objectives for its projects in 2023 in the timing contemplated (if at all); the ability to realize upon any mineralization in a manner that

is economic; the Cariboo project design and ability and timing to complete infrastructure at Cariboo (if at all); the ability and timing

for Cariboo to reach commercial production (if at all); the ability to adapt to changes in gold prices, estimates of costs, e stimates of

planned exploration an d development expenditures; the ability of the Company to obtain further capital on reasonable terms; the

profitability (if at all) of the Company's operations; the Company being a well-positioned gold development company in Canada, USA

and Mexico; sustainability and environmental impacts of operations at the Company's properties; as well as other considerations that

are believed to be a ppropriate in the circumstances; and any other information herein that is not a historical fact may be "forward

looking information". Material assumptions also include, management 's perceptions of historical trends, the ability of exploration

(including drilling) to accurately predict mineralization, budget constraints and access to capital on terms acceptable to the Company,

current conditions and expected future developments, regulatory framework remaining defined and understood, results of further

exploration work to define or expand any mineral resources, as well as other considerations that are believed to be ap propriate in

the circumstances. Osisko Development considers its assumptions to be reasonable based on information currently available, bu t

cautions the reader that their assumptions regarding future events, many of which are beyond the control of Osisko D evelopment,

may ultimately prove to be incorrect since they are subject to risks and uncertainties that affect Osisko Development and its business.

Such risks and uncertainties include, among others, risks relating to capital market conditions and the Comp any's ability to access

capital on terms acceptable to the Company for the contemplated exploration and development at the Company's properties; the

ability to continue current operations and exploration; regulatory framework and presence of laws and regulations that may impose

restrictions on mining ; the ability of exploration activities (including drill results) to accurately predict mineralization; errors in

management's geological modelling; the ability to expand operations or complete further explorati on activities; the timing and ability

of the Company to obtain required approvals and permits ; the results of exploration activities; risks relating to exploration,

development and mining activities; the global economic climate; metal and commodity prices; fluctuations in the currency markets;

dilution; environmental risks; and community , non-governmental and governmental actions and the impact of stakeholder actions.

Readers are urged to consult the disclosure provided under the heading "Risk Factors" in the Company's annual information form

for the year ended December 31, 202 2 as well as the financial statements and MD&A which ha ve been filed on SEDAR +

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(www.sedarplus.ca) under Osisko Development 's issuer profile and on the SEC 's EDGAR website (www.sec.gov) , for further

information regarding the risks and other factors applicable to the exploration results. Although the Company 's 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 up date

any forward-looking statements, whether as a result of new information, future events or results or otherwise, exce pt as required by

law. Forward-looking statements are not guarantees of performance and t here 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 antici pated 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.