Osisko Development Corp. (TSX-V-ODV) is pleased to announce drilling results from the category conversion drill program campaign at its Cariboo Gold Project in central British Columbia.

This news release discusses the final assay results from the 2020 exploration and delineation drill campaign on Valley (Cow Mountain), Mosquito and Shaft Zones (Island Mountain) and includes holes CM-20-100 to CM-20-105 and IM-20-036 to IM-20-061 (Table 1). Detailed drilling results, drill hole location plan maps and vertical sections are presented at the end of this release. The infill drilling results continue to demonstrate continuity and expansion of modelled vein corridors. Drilling highlights include 6.97 g/t Au over 6.50 g/t Au and 7.73 g/t Au over 13.00 meters in hole CM-20-100. Hole CM-20-100 confirmed anomalous gold values within multiple modelled vein corridors (Figure 2). On Island Mountain, Shaft Zone highlights included 11.48 g/t Au over 8.35 meters in hole IM-20-039 and on Mosquito Creek Zone 22.76 g/t Au over 7.00 meters in hole IM-20-053 (Figure 3). The modelled vein corridors remain open at depth and are currently being drill tested with four diamond drill rigs. A total of ten rigs are currently active on Cariboo.

Chris Lodder, President of Osisko Development commented, “These consistent drill results continue to demonstrate the strong potential for resource conversion within the Valley Zone and on the Island Mountain deposits which remain open along strike and at depth. Importantly, the Valley Zone’s present dimensions are starting to compare to the Shaft zone which host the majority of our present resources in the Cariboo Gold Project”.

Further highlights from drilling are presented below.

Recent Drilling Highlights:

• CM-20-100: 6.97 g/t Au over 6.50 meters
• CM-20-100: 7.73 g/t Au over 13.00 meters including 35.50 g/t Au over 0.85 meter
• CM-20-101: 30.70 g/t Au over 1.35 meters
• CM-20-102: 5.62 g/t Au over 9.45 meters including 28.10 g/t Au over 0.50 meter
• IM-20-037: 7.14 g/t Au over 5.05 meters
• IM-20-037: 15.45 g/t Au over 4.50 meters including 56.20 g/t Au over 0.50 meter
• IM-20-039: 17.84 g/t Au over 4.30 meters including 42.30 g/t Au over 1.25 meters
• IM-20-039: 11.48 g/t Au over 8.35 meters including 66.50 g/t Au over 0.65 meter
• IM-20-041: 7.18 g/t Au over 4.75 meters
• IM-20-043: 12.36 g/t Au over 6.75 meters including 40.60 g/t Au over 0.75 meter
• IM-20-050: 46.60 g/t Au over 0.85 meter
• IM-20-053: 22.76 g/t Au over 7.00 meters including 47.00 g/t Au over 1.50 meters
• IM-20-053: 24.73 g/t Au over 2.50 meters including 59.70 g/t Au over 1.00 meter
• IM-20-059: 28.10 g/t Au over 1.50 meter
• IM-20-059: 9.31 g/t Au over 6.00 meters
• IM-20-061: 23.70 g/t Au over 1.50 meters

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’s folds 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.

Figure 1: Cariboo Deposit Areas with drill locations is available at

https://www.globenewswire.com/NewsRoom/AttachmentNg/c9753d5a-23e7-46c1-a11e-693753a13dba

Figure 2: Valley Zone drill hole cross section CM-20-100 is available at

https://www.globenewswire.com/NewsRoom/AttachmentNg/29e6807d-a4e9-4794-8da6-63921a041dd6

Figure 3: Mosquito Creek drill hole cross section IM-20-053 is available at

https://www.globenewswire.com/NewsRoom/AttachmentNg/14c65512-655e-4864-8db2-e9ae32ed71e6

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 4.60 Au g/t for a total of 3.20 million ounces of gold and inferred resource of 21.69 Mt at 3.90 Au g/t for a total of 2.70 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 under the symbol “ODV” on December 2, 2020.

Table 1: Cariboo Gold Project 2020 Length Weighted Drill Hole Gold Composites

Table 2: Drill Hole Locations and Orientations