"I've missed way too much for way too long. and I'm done", Harrison wrote in a Instagram post on Monday.
Harrison split last season between the Steelers and the New England Patriots.
An undrafted free agent out of college, Harrison signed with the Steelers in 2002 and, after a spell in NFL Europe with the Rhein Fire in 2003, returned to Pittsburgh in 2004 and began to make his presence felt.More news: In Karnataka, Congress workers protest, destroy party office over distribution of tickets
You would perhaps forgive most National Football League players for taking some time off from working out at the end of a 15-year career, but James Harrison never was most players.
Harrison's physical play at times ran him into trouble with the league office.More news: Choosing Between Twenty-First Century Fox, Inc. (FOXA) and HollyFrontier Corporation (HFC)
Harrison was a fixture of the Steelers defense for over a decade and delivered one of the most memorable plays in Super Bowl history with his pick-six in the final seconds of the first half in Super Bowl XLIII.
Harrison announced his retirement on Instagram. He had 10 tackles, 3.5 sacks, three forced fumbles and an interception that day against Baltimore. He played sparingly for much of 2017 and the Steelers granted him his release in December.
The Patriots and Harrison had been in contact earlier this offseason about a possible return, but those talks never materialized into a new contract.More news: 7 inmates killed in SC prison altercation