The retired NFL legend only bought the place a few years ago -- but felt it was time to move and we're told he made about $400,000 in profit after selling the place with Douglas Elliman agent George Sarkis.
It's got everything a Boston superstar could want -- a 2,100 square foot penthouse with a sick rooftop deck with a BBQ area ... and walking distance from bars and restaurants in the Seaport District!
Gronk's decor is pretty sweet, too -- the 29-year-old hung a ton of sports memorabilia on the walls that clearly meant a lot to him .