Both players signed one-year deals. The team announced the deals Thursday.
They are the latest moves to improve a secondary looking to replace long-time starting cornerback Chris Gamble, who was released in a salary cap move. Carolina previously signed unrestricted free agent cornerbacks D.J. Moore and Drayton Florence.
Panthers coach Ron Rivera says, "Mitchell should provide competition in the secondary and we know Captain is a tough, hard-nosed competitor capable of making big plays."
Munnerlyn played in all 16 games with 11 starts for the Panthers in 2012.
Mitchell joins the Panthers after playing the first four seasons of his career with the Raiders. He has nine career starts.