Osisko Secondary Crusher Installation Completed

MONTREAL, QUEBEC--(Marketwire - Aug. 3, 2012) - Osisko Mining Corporation (the "Company" or "Osisko") (TSX:OSK)(FRANKFURT:EWX) is pleased to report the successful completion of the installation of the second XL 2000 cone crusher at its flagship Canadian Malartic Mine. Installation and protocol testing were completed in the last half of July.

Daily throughput rates at the Canadian Malartic mill averaged slightly above 46,800 tonnes per day over the last five days of July.

Osisko President and CEO Sean Roosen commented: "We have made good progress at Canadian Malartic in the past three months. The completion of the secondary crusher is an important moment in the move towards the end of the Canadian Malartic ramp up phase."

About Osisko Mining Corporation

Osisko Mining Corporation operates the Canadian Malartic Gold Mine in Malartic, Quebec and is pursuing exploration on a number of properties, including the Hammond Reef Gold Project in Northern Ontario.

Mr. Luc Lessard, Eng., Senior Vice-President and COO of Osisko, is the Qualified Person who has reviewed this news release and is responsible for the technical information reported herein, including verification of the data disclosed.

Forward-Looking Statements

Certain statements contained in this press release may be deemed "forward-looking statements". All statements in this release, other than statements of historical fact, that address events or developments that Osisko expects to occur, are forward looking statements. Forward looking statements are statements that are not historical facts and are generally, but not always, identified by the words "expects", "plans", "anticipates", "believes", "intends", "estimates", "projects", "potential", "scheduled" and similar expressions, or that events or conditions "will", "would", "may", "could" or "should" occur including, without limitation, further development of its Hammond Reef project and increasing of throughput at the mill to achieve design capacity at its Canadian Malartic Mine, timely installation of the pre-crush circuit, compliance with noise regulations, increasing of mining fleet availability, increasing of production. Although Osisko believes the expectations expressed in such forward-looking statements are based on reasonable assumptions, including, without limitation, that all technical, economical and financial conditions will be met in order to warrant further development of its Hammond Reef project and that the diligent ongoing optimizing of its operations at Canadian Malartic mine will be achieved and will, accordingly, improve its operating performance, such statements are not guarantees of future performance and actual results may differ materially from those in forward looking statements.

Factors that could cause the actual results to differ materially from those in forward-looking statements include gold prices, access to skilled consultants, mining development personnel, results of exploration and development activities, Osisko's limited experience with production and development stage mining operations, uninsured risks, regulatory changes, defects in title, availability of personnel, materials and equipment, timeliness of government approvals, actual performance of facilities, equipment and processes relative to specifications and expectations, unanticipated environmental impacts on operations market prices, continued availability of capital and financing and general economic, market or business conditions. These factors are discussed in greater detail in Osisko's most recent Annual Information Form and in the most recent Management Discussion and Analysis filed on SEDAR, which also provide additional general assumptions in connection with these statements. Osisko cautions that the foregoing list of important factors is not exhaustive. Investors and others who base themselves on forward-looking statements should carefully consider the above factors as well as the uncertainties they represent and the risk they entail. Osisko believes that the expectations reflected in those forward-looking statements are reasonable, but no assurance can be given that these expectations will prove to be correct and such forward-looking statements included in this press release should not be unduly relied upon. These statements speak only as of the date of this press release.