Osisko Development Corp. (TSX-V:ODV) is pleased to announce new drilling results from the exploration and delineation program on the Island Mountain, Mosquito Creek and Shaft Zone Deposits on the Cariboo Gold Project in central British Columbia.

This news release discusses the assay results from holes IM-20-001 to IM-20-035 drilled on the Mosquito Creek and Shaft Zone in 2020 (Figures 1 to 3). Highlights include 63.20 g/t Au over 3.20 meters in hole IM-20-002 on Shaft Zone including a sample of 181 g/t Au over 0.80 meter. A total of 13,301 meters were drilled in 76 holes on Mosquito and Shaft in 2020 and many of these assays are pending. The Company is currently drilling on Island Mountain with five diamond drill rigs.

Chris Lodder, President of Osisko, commented: “These results demonstrate the high-grade nature of individual veins on Island Mountain and that infill drilling continues to confirm lateral and vertical continuity of the vein corridors.”

Select Island Mountain Highlights:

• IM-20-001: 8.29 g/t Au over 4.60 meters
• IM-20-002: 63.20 g/t Au over 3.20 meters including 62.40 g/t Au over 0.50 meter and 181 g/t Au over 0.80 meter
• IM-20-003: 23.97 g/t Au over 1.85 meters including 69.20 g/t Au over 0.60 meter
• IM-20-012: 25.80 g/t Au over 1.40 meters
• IM-20-017: 16.46 g/t Au over 1.55 meters including 40.50 g/t Au over 0.50 meter
• IM-20-022: 20.60 g/t Au over 1.00 meter
• IM-20-028: 10.99 g/t Au over 2.10 meters including 36.20 g/t Au over 0.50 meter

Mineralized quartz veins on the Cariboo Gold Project are overall sub-vertical dip and northeast strike. Vein corridors are defined as a high-density network of mineralized quartz veins within the axis of the F3 folds and hosted within the sandstones. Vein corridors are modelled at a minimum thickness of 2 meters and individual veins within each corridor range in width from millimeter to several meters. The modelled vein corridors for the resource update includes the internal dilution of the subeconomic sandstone within these vein corridors. These corridors have been defined from surface to a vertical depth averaging 300 meters and remain open for expansion at depth and down plunge. Gold grades are intimately associated with vein-hosted pyrite as well as pyritic, intensely silicified wall rock haloes in close proximity to the veins.

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.

Figure 1: Cariboo Deposit Overview

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Figure 2: Mosquito Creek recent drilling overview

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Figure 3: Shaft Zone recent drilling overview

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Qualified Persons

Per National Instrument 43-101 Standards of Disclosure for Mineral Projects, Maggie Layman, P.Geo. Vice President Exploration of Osisko, 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 well-capitalized and 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 resource 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 (effective date of October 5^th, 2020 and published on SEDAR). 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 second half of 2021. Osisko Development’s project pipeline is complemented by potential near-term production targeted from the San Antonio gold project, located in Sonora Mexico and early exploration stage properties including the Coulon Project and James Bay Properties located in Québec as well as the Guerrero Properties located in Mexico. Osisko Development began trading on the TSX Venture Exchange under the symbol “ODV” on December 2, 2020.

Table 1: Island Mountain Length Weighted Drill Hole Gold Composites

Table 2: Drill Hole Locations and Orientations