A spokesman for the group said, "If Turkey were to relax foreign ownership restrictions, CanWest would have the right to increase its stake to 75%."
It said the deal, which is subject to regulatory approval, is expected to be completed within the next 90 days.
CanWest, which already owns radio stations in Canada and New Zealand, said the station reaches about 45 percent of the Turkish population, including listeners in Istanbul, Ankara and Izmir.
CanWest executive Tom Strike in a statement said the investment is part of the company's strategy of expanding internationally. He noted CanWest was recently awarded a license to launch a new FM radio station in Britain.
Winnipeg, Manitoba-based CanWest is Canada's largest newspaper publisher and owner of the country's Global Television network. It also owns television assets in Australia, New Zealand and Ireland.