OSK-W-17-903 returned 4.97 g/t Au over 7.5 metres related to CN2 FW zone within the Caribou Corridor. This interval corresponds with sericitized intermediate volcanics with traces of disseminated pyrite.

OSK-W-17-903-W1 returned 9.3 g/t Au over 2.0 metres related to CN2 FW zone within the Caribou Corridor. Mineralization is composed of 5% pyrite stringers hosted in a silicified porphyritic felsic intrusion.

OSK-W-17-937 returned 11.9 g/t Au over 2.0 metres related to CS3 zone within the Caribou Corridor. Mineralization is composed of 15-20% pyrite stringers in a partially bleached and sericitized rhyolite. The interval is 40 metres east of OSK-W-17-715 (6.84 g/t Au over 3.0 metres previously reported August 31, 2017).

OSK-W-17-975 intersected 4.31 g/t Au over 7.8 metres in the Caribou Extension and 7.09 g/t Au over 2.2 meters in Zone 27 Extension. The mineralization is composed of up to 5% pyrite stringers, 5% disseminated pyrite hosted in a chloritized or sericitized andesite. This intersection in Zone 27 extends the zone 200 metres to the northeast from the previous resource boundary.

OSK-W-17-985 intersected 9.9 g/t Au over 4.6 metres. Mineralization consists of up to 5% pyrite stringers, 15% disseminated pyrite hosted in a strongly silicified felsic dike with large quartz eyes.

OSK-W-17-989-W2 intersected 5.28 g/t Au over 2.7 metres related to CS3 Zone in the Caribou Corridor. Mineralization is composed of 5% pyrite stringers and 5% disseminated pyrite in a sericitized andesite.

OSK-W-17-990 intersected Zone 27 returning 3.25 g/t Au over 3.3 metres and 26.4 g/t Au over 2.7 metres. Mineralization is composed of 1% pyrite stringers, 1% pyrite fragments, and local visible gold, chalcopyrite, and sphalerite hosted in a sericitized rhyolite.

OSK-W-17-1014 intersected Zone 27 returning 5.22 g/t Au over 2.1 metres. The mineralization is composed of quartz-tourmaline veins with 10% pyrite stringers at the contact between a porphyritic felsic dike and a sericitized rhyolite.

OSK-W-17-1018 intersected Mallard returning 3.55 g/t Au over 5.9 metres. Mineralization corresponds with 3% quartz-tourmaline veins, 2% tourmaline-pyrite veins, 30% pyrite stringers and local visible gold at the contact between the andesite and a sericitized, strongly silicified felsic dike.

OSK-W-17-1028 intersected three zones related to Caribou Extension: 11.6 g/t Au over 3.1 metres, 10.6 g/t Au over 2.3 metres, and 3.12 g/t Au over 3.1 metres. The first and second intervals correspond with silicified andesite with fuchsite containing 15% pyrite (clusters and stringers). The third interval is composed of 15% pyrite stringers and disseminated pyrite within a silicified rhyolite. Those intervals are 50 metres east of OBM-16-701 (5.14 g/t Au over 6.1 metres previously reported August 23, 2016).

OSK-W-17-1035 intersected 4.27 g/t Au over 2.6 metres related to Zone 27. Mineralization is composed of 7% pyrite stringers and pyrite clusters, associated with ptygmatic tourmaline stringer and strong silica patches, hosted in moderately sericitized and silicified rhyolite and felsic intrusive rock.

OSK-W-17-1042 infilled Zone 27: 3.39 g/t Au over 12.2 metres. Mineralization consists of up to 10-15% pyrite stringers and pyrite clusters, with local semi-massive decimetre scale pyrite bands within silica patches alteration hosted in moderately sericitized, silicified felsic intrusion.

OSK-W-17-1052 intersected 3.26 g/t Au over 2.0 metres in the Caribou Extension. Mineralization consists of trace of disseminated pyrite or in stringers hosted in chloritized and hematized andesite.

OSK-W-17-1056 intersected Zone 27 returning 3.89 g/t Au over 3.0 metres and 7.71 g/t Au over 3.7 metres. Mineralization is composed of 5-30% pyrite stringers, and 1% disseminated pyrite hosted in a sericitized, locally silicified rhyolite.

OSK-W-17-1062 infilled Zone 27: 3.25 g/t Au over 5.7 metres. Mineralization consists of 8% pyrite-chlorite stringers, 2% pyrite clusters, 1% pyrite-tourmaline stringers, and traces of pervasive silica flooding hosted in moderately to strongly silicified felsic intrusion.

OSK-W-17-1070 intersected Zone 27 returning 9.58 g/t Au over 2.4 metres. Mineralization is composed of disseminated pyrite in silica flooding patches hosted in a felsic intrusion.

OSK-W-17-1071 intersected Zone 27 on multiple intervals; 7.12 g/t Au over 2.8 metres; 12.1 g/t Au over 2.2 metres; 5.31 g/t Au over 2.0 metres; 9.72 g/t au over 2.8 metres; and 12.2 g/t Au over 2.3 metres. The first interval is composed of semi-massive pyrite and 1% pyrite stringers hosted in a silicified porphyritic felsic intrusion with large quartz eyes. The second and third intervals are composed of up to 4% disseminated pyrite, up to 1% pyrite stringers and trace of chalcopyrite within a strongly sericitized and silicified rhyolite. The two last intervals are at the upper and lower contact of a felsic dike. Mineralization is composed of disseminated pyrite and pyrite stringers.

OSK-W-17-1090 intersected 5.24 g/t Au over 2.3 metres related to Zone 27. Mineralization is composed of traces of pyrite stringers and 2% tourmaline-pyrite veins hosted in a sericitized felsic intrusion.

OSK-W-17-1124 intersected the Mallard Zone returning 18.3 g/t Au over 2.4 metres. Mineralization is composed of 10% pyrite in pervasive silica flooding within a strongly silicified felsic intrusion.

OSK-W-17-1185 intersected 3.61 g/t Au over 2.8 metres. Mineralization is composed of 2% disseminated pyrite, 1% pyrite-stringers and 2% pyrite-tourmaline stringers in moderately silicified and sericitized felsic porphyritic intrusive. This interval is potentially a new zone in the possible north-east extension of Zone 27. Geometry is yet to be determined.

OSK-W-17-1207 intersected the Mallard Zone returning 6.17 g/t au over 2.0 metres. Mineralization is composed of 4% pyrite as stringers and clusters in association with quartz-carbonate veining and weakly developed crustiform vein hosted in andesite with moderate patchy sericitization and chloritization.

OSK-W-17-1210 intersected 4.26 g/t Au over 2.1 metres in the Caribou Extension. Mineralization is composed 3% of pyrite-tourmaline stringers, 2% of pyrite clusters and 2% disseminated pyrite in a strongly silicified fragmental andesite with fragments of rhyolite and local fuchsite.

OSK-W-17-1218 intersected 6.88 g/t Au over 2.0 metres. Mineralization is in the Caribou Extension and is composed of 15% of pyrite stringers, 3% disseminated pyrite, 2% pyrite clusters,1% disseminated chalcopyrite and tourmaline dismembered ptygmatic veins, all hosted in a sericitized, silicified rhyolite.

OSK-W-17-1220 intersected Zone 27 returning 12.3 g/t Au over 2.6 metres. Mineralization corresponds with a semi-massive band of pyrite (40%) with disseminated tourmaline hosted in a silicified rhyolite.

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 ("NI 43-101").

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 ("QA/QC") 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 $240 million in cash and investments.

Cautionary Note Regarding Forward-Looking Information

This news release contains "forward-looking information" within the meaning of the applicable Canadian securities legislation that is based on expectations, estimates, projections and interpretations as at the date of this news release. The information in this news release about the Windfall Lake gold deposit being one of the highest grade resource-stage gold projects in Canada; the current 800,000 metre drill program; the significance of new results from the ongoing drill program at the Windfall Lake gold project; the significance of assay results presented in this press release; the type of drilling included in the drill program (definition drilling, expansion drilling to the NE of the main deposit and adjacent Lynx deposit, and exploration drilling on the greater deposit and Urban-Barry project area); potential mineralization; the potential to extend mineralization up and down-plunge and at depth at the Windfall Lake gold deposit; the ability to realize upon any mineralization in a manner that is economic; the ability to complete any proposed exploration activities and the results of such activities, including the continuity or extension of any mineralization; and any other information herein that is not a historical fact may be "forward-looking information". Any statement that involves discussions with respect to predictions, expectations, interpretations, beliefs, plans, projections, objectives, assumptions, future events or performance (often but not always using phrases such as "expects", or "does not expect", "is expected", "interpreted", "management's view", "anticipates" or "does not anticipate", "plans", "budget", "scheduled", "forecasts", "estimates", "believes" or "intends" or variations of such words and phrases or stating that certain actions, events or results "may" or "could", "would", "might" or "will" be taken to occur or be achieved) are not statements of historical fact and may be forward-looking information and are intended to identify forward-looking information.

This forward-looking information is based on reasonable assumptions and estimates of management of the Corporation. at the time it was made, involves known and unknown risks, uncertainties and other factors which may cause the actual results, performance or achievements of Osisko to be materially different from any future results, performance or achievements expressed or implied by such forward-looking information. Such factors 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 Osisko to complete further exploration activities, including drilling; property interests in the Windfall Lake gold project; the ability of the Corporation to obtain required approvals and complete transactions on terms announced; the results of exploration activities; risks relating to mining activities; the global economic climate; metal prices; dilution; environmental risks; and community and non-governmental actions. Although the forward-looking information contained in this news release is based upon what management believes, or believed at the time, to be reasonable assumptions. Osisko cannot assure shareholders and prospective purchasers of securities of the Corporation that actual results will be consistent with such forward-looking information, as there may be other factors that cause results not to be as anticipated, estimated or intended, and neither Osisko nor any other person assumes responsibility for the accuracy and completeness of any such forward-looking information, Osisko does not undertake, and assumes no obligation, to update or revise any such forward-looking statements or forward-looking information contained herein to reflect new events or circumstances, except as may be required by law.