Mitchell, acquired in a 2010 trade from Minnesota, had a disappointing season in 2011, losing his starting job to Emmanuel Stephens.
Mitchell's release was expected after the Browns signed free agent Frostee Rucker from Cincinnati as well as Parker, who played for Philadelphia last season. Parker will be reunited with Browns general manager Tom Heckert. The two worked together with the Eagles.
Heckert called Parker "one of the toughest players I've ever been around."