Osisko Development Intersects 10.85 g/t Au over 14.25 meters and other High-Grade Samples of 91.6 g/t Au, 90.7 g/t Au, 126.5 g/t Au, 120.0 g/t Au, 94.1 g/t Au, 201.0 g/t Au, 278.0 g/t Au and 113.0 g/t Au at Valley

Summary

• A total of 47,500 meters were drilled in 109 holes in the Valley Deposit in 2021.
• This news release includes assay results from holes CM-21-061-1 to CM-21-093 (Figures 1 and 2).
• Visible gold was observed in many holes including assays of 60 g/t Au over 0.60 meter in hole CM-21-063, 126.50 g/t Au over 0.50 meter in CM-21-068, 120.00 g/t Au over 0.50 meter and 94.10 g/t Au over 0.65 meter in CM-21-084, 201.00 g/t Au over 0.50 meter CM-21-086 and 278.00 g/t Au over 0.50 meter in CM-21-088 (Figure 3).
• CM-21-078 intersected a vein corridor that assayed 85 g/t Au over 14.25 meters and included higher grade samples of 23.20 g/t Au over 0.70 meter, 32.10 g/t Au over 0.80 meter, 23.90 g/t Au over 0.50 meter, 25.70 g/t Au over 0.50 meter, 23.40 g/t Au over 0.50 meter and 22.90 g/t Au over 0.50 meter.  
• Detailed drilling results and a drill hole location plan map are presented at the end of this release.

Assay Highlights

• 51 g/t Au over 11.65 meters in hole CM-21-061-1
• 08 g/t Au over 0.60 meter in hole CM-21-061-1
• 60 g/t Au over 0.60 meter in hole CM-21-063
• 62 g/t Au over 1.60 meters in hole CM-21-064
• 44 g/t Au over 5.20 meters in hole CM-21-064
• 70 g/t Au over 0.50 meter in hole CM-21-066
• 03 g/t Au over 8.20 meters in hole CM-21-067
• 50 g/t Au over 0.50 meter in hole CM-21-068
• 57 g/t Au over 13.55 meters in hole CM-21-069 including
• 20 g/t Au over 0.75 meter
• 11 g/t Au over 6.25 meters in hole CM-21-070
• 89 g/t Au over 16.90 meters in hole CM-21-071
• 85 g/t Au over 7.55 meters in hole CM-21-076
• 85 g/t Au over 14.25 meters in hole CM-21-078
• 80 g/t Au over 1.15 meters in hole CM-21-084 including
• 00 g/t Au over 0.50 meter
• 01 g/t Au over 4.80 meters in hole CM-21-084 including
• 10 g/t Au over 0.65 meter
• 74 g/t Au over 3.80 meters in hole CM-21-085
• 73 g/t Au over 2.50 meters in hole CM-21-086
• 00 g/t Au over 0.50 meter in hole CM-21-086
• 98 g/t Au over 8.10 meters in hole CM-21-087
• 40 g/t Au over 4.15 meters in hole CM-21-087 including
• 00 g/t Au over 0.50 meter                                               
• 87 g/t Au over 1.50 meters in hole CM-21-088 including
• 00 g/t Au over 0.50 meter
• 00 g/t Au over 0.50 meter in hole CM-21-089
• 78 g/t Au over 8.00 meters in hole CM-21-089
• 44 g/t Au over 4.90 meters in hole CM-21-091
• 89 g/t Au over 8.70 meters in hole CM-21-092
• 47 g/t Au over 1.90 meters in hole CM-21-093 including
• 30 g/t Au over 0.90 meter
• 57 g/t Au over 5.35 meters in hole CM-21-093
• 72 g/t Au over 2.60 meters in hole CM-21-093
• 80 g/t Au over 0.60 meter in hole CM-21-093
• 89 g/t Au over 8.60 meters in hole CM-21-093

Maggie Layman, Vice President of Exploration for Osisko Development commented, “The 2021 category conversion and exploration program at the Valley Deposit was successful in delineating and expanding known vein corridors with high grade gold samples to support our feasibility study and ongoing mine planning, increasing confidence in the project and generating further interest for exploration within the main area and beyond.”

Vein corridors are defined as high-density networks of mineralized quartz veins within the axis of the deposit’s last folding event. These mineralized structures are predominantly hosted within a brittle meta-sandstone or calcareous meta-sandstone. Vein corridors are modelled at a minimum thickness of 2.00 meters and average about 4.50 meters true width. Individual mineralized veins within these corridors have widths varying from centimeters to several meters and strike lengths from a few meters to over 50 meters. These corridors have been defined from surface to a vertical depth averaging 300 meters and remain open for expansion at depth and along strike. Gold grades are intimately associated with quartz vein-hosted pyrite as well as pyritic, intensely silicified wall rock vein selvages.

True widths are estimated to be 60% to 75% of reported core length intervals. Intervals not recovered by drilling were assigned zero grade. Top cuts have not been applied to high grade assays. Complete assay highlights are presented in Table 1, drill hole locations are listed in Table 2.

Qualified Persons

Per National Instrument 43-101 Standards of Disclosure for Mineral Projects, Maggie Layman, P.Geo. Vice President Exploration of Osisko Development Corp., is a Qualified Person and has prepared, validated, and approved the technical and scientific content of this news release.

Quality Assurance – Quality Control

Once received from the drill and processed, all drill core samples are sawn in half, labelled and bagged.  The remaining drill core is subsequently stored on site at a secured facility in Wells, BC.  Numbered security tags are applied to lab shipments for chain of custody requirements.  Quality control (“QC”) samples are inserted at regular intervals in the sample stream, including blanks and reference materials with all sample shipments to monitor laboratory performance. The QAQC program was designed and approved by Lynda Bloom, P.Geo. of Analytical Solutions Ltd.

Drill core samples are submitted to ALS Geochemistry’s analytical facility in North Vancouver, British Columbia for preparation and analysis. The ALS facility is accredited to the ISO/IEC 17025 standard for gold assays and all analytical methods include quality control materials at set frequencies with established data acceptance criteria. The entire sample is crushed, and 250 grams is pulverized. Analysis for gold is by 50g fire assay fusion with atomic absorption (“AAS”) finish with a lower limit of 0.01 ppm and upper limit of 100 ppm. Samples with gold assays greater than 100 ppm are re-analyzed using a 1,000g screen metallic fire assay. A selected number of samples are also analyzed using a 48 multi-elemental geochemical package by a 4-acid digestion, followed by Inductively Coupled Plasma Atomic Emission Spectroscopy (“ICP-AES”) and Inductively Coupled Plasma Mass Spectroscopy (“ICP-MS”).

About Osisko Development Corp.

Osisko Development Corp. is uniquely positioned as a premier gold development company in North America to advance the Cariboo Gold Project and other Canadian and Mexican properties, with the objective of becoming the next mid-tier gold producer. The Cariboo Gold Project, located in central British Columbia, is Osisko Development’s flagship asset with measured and indicated resources of 21.44 Mt at 4.6 Au g/t for a total of 3.2 million ounces of gold and inferred resource of 21.69 Mt at 3.9 Au g/t for a total of 2.7 million ounces of gold (see NI 43-101 Technical Report and mineral resource estimate effective October 5^th, 2020). The considerable exploration potential at depth and along strike distinguishes the Cariboo Gold Project relative to other development assets as does the historically low, all-in discovery costs of US $19 per ounce. The Cariboo Gold Project is advancing through permitting as a 4,750 tonnes per day underground operation with a feasibility study on track for completion in the first half of 2022. Osisko Development’s project pipeline is complemented by potential near-term production targeted from the San Antonio gold project, located in Sonora Mexico. Osisko Development began trading on the TSX Venture Exchange under the symbol “ODV” on December 2, 2020 and 14,789,373 of the Company’s 24,315,223 outstanding share purchase warrants were listed on the TSX Venture Exchange under the symbol “ODV.WT” on October 25, 2021.

For further information, please contact Osisko Development Corp.:

Jean Francois Lemonde

VP Investor Relations

jflemonde@osiskodev.com

Tel: 514-299-4926

In Europe:

Swiss Resource Capital AG

Jochen Staiger

info@resource-capital.ch

www.resource-capital.ch

Forward-looking Statements

Certain statements contained in this press release may be deemed “forward‐looking statements” within the meaning of applicable Canadian and U.S. securities laws. 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 that were applied in drawing a conclusion or making a forecast or projection, including management’s perceptions of historical trends, current conditions and expected future developments, results of further exploration work to define and expand mineral resources, expected conclusions of optimization studies, that vein corridors continue to be defined as a high-density network of mineralized quartz within the axis of the last folding event and hosted within the sandstones and that the deposit remains open for expansion at depth and down plunge, as well as other considerations that are believed to be appropriate in the circumstances. Osisko Development considers its assumptions to be reasonable based on information currently available, but cautions the reader that their assumptions regarding future events, many of which are beyond the control of Osisko Development, 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 the ability of exploration activities (including drill results) to accurately predict mineralization; errors in management’s geological modelling; the ability of to complete further exploration activities, including drilling; property and stream interests in the San Antonio gold project; the ability of the Corporation to obtain required approvals; the results of exploration activities; risks relating to exploration, development and mining activities; the global economic climate; metal prices; dilution; environmental risks; and community and non-governmental actions and the responses of relevant governments to the COVID-19 outbreak and the effectiveness of such responses.

For additional information with respect to these and other factors and assumptions underlying the forward‐ looking statements made in this news release concerning Osisko Development, see the Filing Statement available electronically on SEDAR (www.sedar.com) under Osisko Development’s issuer profile. The forward‐looking statements set forth herein concerning Osisko Development reflect management’s expectations as at the date of this news release and are subject to change after such date. Osisko Development disclaims any intention or obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise, other than as required by law.

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.