Osisko Mining Corporation Enters Into a Bought Deal Agreement for Gross Proceeds of C$130,025,000

MONTREAL, QUEBEC--(Marketwire - Aug. 12, 2009) - THIS NEWS RELEASE IS INTENDED FOR DISTRIBUTION IN CANADA ONLY AND IS NOT AUTHORIZED FOR DISTRIBUTION TO UNITED STATES NEWSWIRE SERVICES OR FOR DISSEMINATION IN THE UNITED STATES. Osisko Mining Corporation ("Osisko" or the "Company") OSKEWX has today entered into an agreement with a syndicate of underwriters led by Thomas Weisel Partners Canada Inc. and BMO Capital Markets (the "Underwriters") under which the Underwriters have agreed to buy 18,575,000 common shares (the "Common Shares") from Osisko on a bought-deal basis and sell them to the public at a price of C$7.00 per Common Share. The Company has also granted to the Underwriters an over-allotment option to purchase an additional 2,786,250 Common Shares at the same price, exercisable in whole or in part, for a period of 30 days on or following the closing date. The gross proceeds raised from the offering will be C$130,025,000 (C$149,528,750 if the over-allotment option is exercised). The offering is subject to the approval of the TSX. The Common Shares will be offered in British Columbia, Alberta, Saskatchewan, Manitoba, Ontario and Quebec by short form prospectus, and in such other jurisdictions, including the United States and in those jurisdictions outside of Canada which are agreed to by the Company and the Underwriters, where the Common Shares can be issued on a private placement basis, exempt from any prospectus, registration or other similar requirements. The offering is expected to close on or about September 1, 2009. Osisko intends to use the net proceeds of the offering to fund the development of the Malartic project and for general corporate purposes. The securities being offered have not, nor will they be registered under the United States Securities Act of 1933, as amended, and may not be offered or sold within the United States or to, or for the account or benefit of, U.S. persons absent U.S. registration or an applicable exemption from the U.S. registration requirements. This release does not constitute an offer for sale of securities in the United States.