On New Year's Day, 1976, Apollo Creed has successfully defended his heavyweight title in a split decision, he and Rocky are taken to the same hospital. Apollo challenges Rocky to a rematch, but Rocky declines and officially retires from boxing. His girlfriend Adrian supports his choice, and so do his doctors, who reveal he will require surgery for a detached retina, which could lead to permanent blindness. In a private moment, Rocky goes to see a recuperating Apollo, and wants a truthful response if Apollo gave his all in the fight, to which Creed agrees. After Rocky is released from the hospital, he enjoys the benefits of his life's changes: Rocky's new fame attracts an agent who sees Rocky as a potential endorsement and sponsorship goldmine, and his sudden wealth encourages him to propose to Adrian. She happily accepts, and they marry in a small ceremony. Soon after, Rocky and Adrian happily learn that Adrian is pregnant.
Meanwhile, fueled by hate mail, Apollo becomes obsessed with the idea that a rematch is the only way to prove that Rocky's performance was simply a fluke. Determined to rectify his boxing career's only blemish, Apollo ignores all pleas by his friends and family to forget the fight and move on to other potential opponents, and instead demands his team do whatever necessary to goad Rocky out of his hiatus and have a rematch with him.
Rocky at first seems unaffected by Apollo's smear campaign, but his inexperience with money causes him to run into financial problems. After largely unsuccessful attempts to find employment, Rocky visits Mickey Goldmill, his trainer and manager, at his gym to talk about the possibility of returning to boxing. At first, Mickey declines, concerned about Rocky's health, but he soon accepts after Apollo publicly insults Rocky. Adrian confronts Rocky about the danger of returning to boxing and reminds him of the risk to his eyesight. Rocky argues he knows nothing else, so this is the only way he can provide. Adrian, furious at Rocky for breaking his promise, refuses to support him.
Rocky and Mickey begin training, but Rocky is not focused on the job at hand due to Adrian's disapproval. Adrian's brother, Paulie, confronts his sister about not supporting her husband, but she faints during the confrontation and is rushed to the hospital, where she goes into labor. Despite being premature, the baby is healthy, but Adrian falls into a coma. Rocky blames himself for what has happened and refuses to leave Adrian's bedside until she wakes up, and will not go to see his new baby until they can see it together. When Adrian comes out of her coma, she finds Rocky by her bedside, and the couple are shown their new baby, a boy, which they name Rocky Jr. Adrian gives her blessing to the rematch, and Rocky quickly gets into shape for the match. When he makes the same training run that he did in the first film, ending at the "Rocky Steps" at the Philadelphia Museum of Art, he is now followed by a crowd of children, some of whom followed him with his consent near the start of his run.
The night of the match arrives, and Apollo has made a public goal of beating Rocky in no more than two rounds to prove the first match going the full fifteen rounds was a fluke. Rocky, fighting right-handed to protect his eye instead of his natural southpaw, is not able to mount much of an offensive effort through the first two rounds but manages to survive them, disproving Apollo's theory that the first fight's result was a fluke. Although the match once again progresses to the full fifteen rounds, the judges have given Creed so many points Rocky would once again lose if the rounds expire. However, Apollo's obsession with knocking Rocky out (against the advice of his corner men) leads him to trade blows with Rocky rather than play it safe and win by decision.
In the final round, Rocky, who switched tactics and is fighting left-handed again, lands a devastating blow on Apollo that knocks him down, but an exhausted Rocky loses his balance and collapses as well. Just before the match is about to end in a draw (titles cannot change hands in this manner), Rocky manages to get back up by the count of nine. Rocky wins the match by a knockout and becomes the heavyweight champion of the world. In his post-fight announcement, Rocky, who has won back the respect of his fans and Adrian, humbly thanks Apollo for the match and ends by hoisting the world championship belt and screaming, "Yo, Adrian, I did it!"
Why does Rocky run into financial problems?
Inexperience with money