Sirius XM said Tuesday that the 69-year-old Karmazin will leave Feb. 1. He will also leave the company's board.
Karmazin has been Sirius XM's CEO since 2004. There has been speculation Karmazin would leave the company after an expected takeover by Liberty Media Corp., which is seeking a controlling interest in the satellite radio provider.
Liberty has amassed a 47.3 per cent stake in Sirius XM, and the Federal Communications Commission is currently considering Liberty's proposal to take control of the company.
Karmazin's contract expires at the end of this year, but he will stay for another month to help transition a new CEO.
The company's board has formed a committee to search for a new CEO.