The team made the announcement Saturday.
Pittsburgh general manager Kevin Colbert said in a statement that "James has been an integral part of our success during his years in Pittsburgh and has helped us win two Lombardi trophies during that time. We appreciate all of his efforts and wish him the best."
Harrison was voted AP's NFL Defensive Player of the Year in 2008 after setting a team record with 16 sacks. The five-time Pro Bowl player has the longest interception return in Super Bowl history, a 100-yarder for a score against the Arizona Cardinals in 2009.