The 2008 defensive player of the year was told over the weekend that he is not part of their plans for the 2013 season.
The 34-year-old told NFL Total Access: "We just couldn't come to terms with something [the Steelers] were comfortable with and I was comfortable with. It's a business, and we had to part ways."
Steelers general manager Kevin Colbert said in a statement: "We have informed James Harrison that we have released him. 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 recorded six sacks and two forced fumbles during the 2012 season.