It's been years since boxer Rocky Balboa (SYLVESTER STALLONE) was heavyweight champion of the world. With his wife and longtime manager now dead, Rocky's moved on to running a neighborhood Philly restaurant where he enjoys entertaining the patrons with his tales of old.
His annual tour of reliving the past by visiting his old haunts, however, no longer sits well with his former brother-in-law, Paulie (BURT YOUNG) who has a more negative outlook on life than his more famous relative. That old fame has also led to something of an estranged relationship with his adult son, Rocky Jr. (MILO VENTIMIGLIA), who feels he's never been able to get out from under the shadow of his hometown-favorite father.
Accordingly, he isn't happy when Rocky decides to reenter the ring one last time. It seems current heavyweight champion Mason "The Line" Dixon (ANTONIO TARVER) could use some good publicity, so his camp has come up with the idea of an exhibition bout. Despite seemingly being too old, Rocky still has the fire in him, and thus proceeds to train for the big fight.
At the same time, he befriends and then finally employs Marie (GERALDINE HUGHES), a local woman he once knew as a child who now has a teenager, Steps (JAMES FRANCIS KELLY III), of her own. She's somewhat suspicious of why he's being so nice to them, but he seems to enjoy their platonic friendship. That and other elements serve as inspiration for him as he prepares to enter the ring and take on his much younger and formidable competitor.