Osisko Development Corp. (TSX-V:ODV) is pleased to announce drilling results from the 200,000-meter 2021 exploration and category conversion drill program campaign at its Cariboo Gold Project in central British Columbia. A total of ten diamond drill rigs are currently active on the Project.

Drilling Summary

• 41,000 meters in 134 holes have been drilled at Island Mountain thus far in 2021.
• Island Mountain encompasses both the Mosquito Creek and Shaft Zone deposits (Figure 1).
• Recent assay results include holes IM-21-024 to IM-21-036.
• Drilling highlights include 35.25 g/t Au over 11.00 meters in hole IM-21-024 (Figure 2) at Mosquito Creek within a silicified sandstone to calcareous sandstone unit with 5% pyrite hosted in axial planar veins and intersected by fault structures.
• Shaft Zone hole IM-21-035 assayed 18.80 g/t Au over 6.20 meters and included multiple high-grade samples such as 102.00 g/t Au over 0.70 meter and is a mineralized vein corridor with replacement mineralization (Figure 3).
• Detailed drilling results and a drill hole location plan map are presented at the end of this release.

Recent Drilling Highlights:

• 35.25 g/t Au over 11.00 metres in hole IM-21-024 including
• 239.00 g/t Au over 1.50 metres
• 11.14 g/t Au over 9.40 metres in hole IM-21-029 including
• 66.30 g/t Au over 0.50 meter
• 21.69 g/t Au over 6.35 meters in hole IM-21-031 including
• 53.00 g/t Au over 1.00 meter and
• 50.10 g/t Au over 0.70 meter
• 24.60 g/t Au over 1.20 meters in hole IM-21-033
• 18.80 g/t Au over 6.20 meters in hole IM-21-035 including
• 102.00 g/t Au over 0.70 meter and
• 33.10 g/t Au over 0.75 meter
• 21.11 g/t Au over 2.80 meters in hole IM-21-035 including
• 63.20 g/t Au over 0.75 meters

Chris Lodder, President of Osisko Development commented, “Today’s results from these drill holes, including two intercepts greater than 100 g/t gold, continue to demonstrate high-grade mineralization at both the Mosquito and Shaft Deposits and multiple mineralized vein corridors per drill hole.”

Mineralized quartz veins on Cariboo 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 last folding event and hosted within a brittle meta-sandstone or calcareous meta-sandstone. Vein corridors are modelled at a minimum thickness of 2 meters and average about 4.5 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 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.

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 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 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 for resource 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 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 on December 2, 2020.

Table 1: Cariboo Gold Project 2021 Length Weighted Drill Hole Gold Composites

Table 2: Drill Hole Locations and Orientations

Figures accompanying this announcement is available at

https://www.globenewswire.com/NewsRoom/AttachmentNg/5bd84a90-3486-44b0-9b4c-f2bfc2a7b0ca

https://www.globenewswire.com/NewsRoom/AttachmentNg/d66c53e4-f44f-4312-8748-ec3179a24a32

https://www.globenewswire.com/NewsRoom/AttachmentNg/3cfa7f61-395b-40b6-88cf-c9b015a2cb2c