Harrison, 39, posted a collage of pictures of his two sons and noted he's "missed way too much for way too long ... and I'm done".
Harrison, a five-time Pro Bowler, had said ahead of the Super Bowl that he had hoped to play another season or two, but citing family, made a decision to retire instead.
Harrison played almost his entire career with the Steelers, collecting 80.5 of his 84.5 career sacks while wearing black and gold, a franchise record.
Oil, gold open lower in spite of Syria strikes; Russia retaliation eyed
The mechanism would look at cases where the OPCW fact-finding mission has established chemical weapons were used or likely used. Russian and Iranian military help over the past three years has allowed Assad to crush the rebel threat to topple him.
Harrison helped the Patriots reach the Super Bowl, where they ultimately lost to the Philadelphia Eagles.
James Harrison calls it quits again. He announced in August he was done, but Harrison returned to the field in September.
Harrison's physical play at times ran him into trouble with the league office.
A year ago, the Steel City was rooting for their aging veteran to pound out one more season and hang up the cleats in the locker room he established himself in. He appeared in five games with the Steelers before being cut by the team and then played in one game regular season game and three postseason contests with New England. The Ravens sent him to NFL Europe before eventually releasing him.