Osisko Mining Inc. (TSX:OSK) is pleased to provide new results from the ongoing drill program at its 100% owned Windfall Lake gold project located in the Abitibi greenstone belt, Urban township, Eeyou Istchee James Bay, Québec. The 800,000 metre drill program combines definition, expansion and exploration drilling in and around the main Windfall gold deposit and the adjacent Lynx deposit (located immediately NE of Windfall).

Significant new analytical results from 16 intercepts in 5 drill holes and 5 wedges focused on infill and expansion drilling in the Lynx deposit are presented below. Osisko continues to extend the known Lynx zones of mineralization through the application of the Windfall geological model and as the density of drilling increases.

Highlights from the new results include: 403 g/t Au over 2.7 metres in OSK-W-18-1412-W1; 151 g/t Au over 2.2 metres in OSK-W-18-1414-W2, 40.1 g/t Au over 2.0 metres in OSK-W-17-1363, and 36.3 g/t Au over 2.0 metres in OSK-W-18-1436. Maps showing hole locations and full analytical results are available at www.osiskomining.com.

President and CEO John Burzynski commented: “We continue to see good results from our drilling at Lynx and are looking forward to our initial mineral resource estimate which is on schedule for delivery in May. The Lynx Corridor was discovered by the Osisko team just a year ago and has been traced out over a length of almost two kilometres and remains open along strike. As we closed the database for the mineral resource calculation in mid-March, today’s results will not be included but will add to the upside potential of the Lynx deposit as we head towards the feasibility study in early 2019.”

OSK-W-17-1166-W3 intersected three intervals: 6.38 g/t Au over 3.8 metres in Lynx Corridor, 4.06 g/t Au over 2.0 metres and 6.26 g/t Au over 2.0 metres in Lynx 6. The first interval is composed of 2% pyrite clusters and 1% pyrite stringers in a strongly sericitized felsic fragmental intrusion. The second interval is composed of 3% pyrite clusters and one pyrite stringers within a strongly sericitized rhyolite. The last interval is composed of pyrite stringers and pyrite-silica flooding within a weak sericite altered felsic porphyritic dike.

OSK-W-17-1193 intersected two intervals in a shear zone, 200 metres south of Lynx 6 returned 5.66 g/t Au over 2.2 metres and 11.0 g/t Au over 2.0 metres. In the first interval, mineralization is composed of 3% disseminated pyrrhotite and the second interval is composed of 2% pyrite clusters and pyrrhotite traces. Small quartz veins are with the mineralization and hosted in a sheared, strongly sericitized andesite.

OSK-W-17-1343-W1 intersected 3.32 g/t Au over 3.1 metres in Lynx HW. Mineralization is composed of trace pyrite within moderate sericite altered gabbro.

OSK-W-17-1363 intersected two intervals: 3.28 g/t Au over 2.0 metres in the Lynx HW and 40.1 g/t Au over 2.0 metres in a crustiform vein. In the first interval, mineralization is composed of disseminated pyrite and pyrite stringers within a chloritized rhyolite. The second interval is composed of 7% pyrite stringers and pyrite-silica flooding within a strong chlorite, strong fuchsite and weak silica altered gabbro. The interval is 85 metres down plunge of OSK-W-17-1121 (8.62 g/t over 2.7 metres previously reported Octobre 12, 2017).

OSK-W-17-1379 intersected 5.62 g/t Au over 2.1 metres in Lynx 1. Mineralization is composed of up to 5% pyrite stringers within a strong sericite, chlorite and fuchsite altered felsic porphyritic dike.

OSK-W-17-1413 intersected two intervals in Lynx 4: 5.77 g/t Au over 2.4 metres and 3.83 g/t Au over 2.0 metres. In the first interval, mineralization is composed of 1% disseminated pyrite and 1% pyrite-silica flooding within a strongly silicified, large quartz eyes, felsic porphyritic intrusion. The interval is 100 metres south-west of OSK-W-17-827 (3.63 g/t over 3.0 metres previously reported July 12, 2017). The second interval is composed of disseminated pyrite within a strong chlorite and weak fuchsite altered andesite.

OSK-W-18-923-W1 intersected 3.39 g/t Au over 2.0 metres in Lynx 4. Mineralization is composed of 2% pyrite clusters, 1% pyrite stringers and 1% disseminated pyrite in quartz vein fracture filling. Mineralization is at a sericite and fuchsite altered contact between a gabbro and a rhyolite.

OSK-W-18-1412-W1 intersected two intervals: 403 g/t Au over 2.7 metres and 10.4 g/t Au over 2.0 metres in Lynx 1. The first interval is composed of up to 5% pyrite as stringers, clusters, and disseminated, 2% disseminated chalcopyrite and local visible gold within a moderate sericite, silica and fuchsite altered gabbro. The second interval is composed of up to 10% disseminated pyrite, up to 10% pyrite-tourmaline veins and 5% disseminated pyrite within a moderate silica, moderate sericite and weak fuchsite altered gabbro.

OSK-W-18-1414-W2 intersected 151 g/t Au over 2.2 metres in Lynx 4. Mineralization is composed of 1% pyrite-tourmaline veins, 1% pyrite clusters, up to 8% disseminated pyrite and local visible gold within a strong silica, sericite and fuchsite altered gabbro.

OSK-W-18-1436 intersected 36.3 g/t Au over 2.0 metres in Lynx 2. Mineralization is composed of up to 2% pyrite stringers and 2% ptygmatic quartz-tourmaline veins within strong silica and sericite altered gabbro.

Qualified Person

The scientific and technical content of this news release has been reviewed, prepared and approved by Mr. Louis Grenier, M.Sc.A., P.Geo. (OGQ 800), Project Manager of the Windfall Lake gold project, who is a “qualified person” as defined by National Instrument 43-101 – Standards of Disclosure for Mineral Projects.

Quality Control and Reporting Protocols

True widths determinations are estimated at 65-80% of the reported core length intervals for most of the zones. Assays are uncut except where indicated. Intercepts occur within geological confines of major zones but have not been correlated to individual vein domains at this time. Reported intervals include minimum weighted averages of 3.0 g/t Au diluted over core lengths of at least 2.0 metres. All NQ core assays reported were obtained by either 1-kilogram screen fire assay or standard 50-gram fire-assaying-AA finish or gravimetric finish at ALS Laboratories in Val d’Or, Québec, Thunder Bay and Sudbury, Ontario or Vancouver, British Colombia or Bureau Veritas in Timmins, Ontario. The 1-kilogram screen assay method is selected by the geologist when samples contain coarse gold or present a higher percentage of pyrite than surrounding intervals. Selected samples are also analyzed for multi-elements, including silver, using an Aqua Regia-ICP-AES method at ALS Laboratories. Drill program design, Quality Assurance/Quality Control and interpretation of results is performed by qualified persons employing a QA/QC program consistent with NI 43-101 and industry best practices. Standards and blanks are included with every 20 samples for QA/QC purposes by the Corporation as well as the lab. Approximately 5% of sample pulps are sent to secondary laboratories for check assay.

About the Windfall Lake Gold Deposit

The Windfall Lake gold deposit is located between Val-d’Or and Chibougamau in the Abitibi region of Québec, Canada. The mineral resource defined by the previous operator comprises 2,762,000 tonnes at 8.42 g/t Au (748.000 ounces) in the indicated category and 3,512,000 tonnes at 7.62 g/t Au (860,000 ounces) in the inferred category (sourced from a technical report dated June 10, 2015 entitled “Preliminary Economic Assessment of the Windfall Lake Gold Property, Québec, Canada” with an effective date of April 28, 2015, prepared in accordance with NI 43-101). The Windfall Lake gold deposit is currently one of the highest grade resource-stage gold projects in Canada. The bulk of the mineralization occurs in the Main Zone, a southwest/northeast trending zone of stacked mineralized lenses, measuring approximately 600 metres wide and at least 1,400 metres long. The deposit is well defined from surface to a depth of 500 metres, and remains open along strike and at depth. Mineralization has been identified only 30 metres from surface in some areas and as deep as 870 metres in others, with significant potential to extend mineralization up and down-plunge and at depth.

About Osisko Mining Inc.

Osisko is a mineral exploration company focused on the acquisition, exploration, and development of precious metal resource properties in Canada. Osisko holds a 100% in the high-grade Windfall Lake gold deposit located between Val-d’Or and Chibougamau in Québec and holds a 100% undivided interest in a large area of claims in the surrounding Urban Barry area and nearby Quevillon area (over 3,300 square kilometres), a 100% interest in the Marban project located in the heart of Québec’s prolific Abitibi gold mining district, and properties in the Larder Lake Mining Division in northeast Ontario, including the Jonpol and Garrcon deposits on the Garrison property, the Buffonta past producing mine and the Gold Pike mine property. The Corporation also holds interests and options in a number of additional properties in northern Quebec and Ontario. Osisko continues to be well financed with approximately $190 million in cash and investments (based on figures available as of December 31, 2017).