This inspirational biography begins in November 1988, with Vinny Pazienza Involved in a boxing battle against Roger Mayweather for the WBC World Light Welterweight Title. He arrives late to the weigh-in, as he has been riding a stationary bicycle in order to make the weight limit. Vinny's final weight is 140 pounds even, which qualifies him for the fight.
Instead of resting up for the fight, Vinny spends the night at a casino. The following day, he loses to Mayweather. At one point during the fight, Vinny is hit after the bell. His boxing manager Lou Duva causes a scene by going after Mayweather, but is punched as a result. Following the match, Duva tells the media that Vinny should retire from boxing. This angers Vinny's father Angelo (who serves as his coach), and he confronts Duva. In the ensuing argument, Vinny announces that he wants another fight, and hires Kevin Rooney as his coach.
Angelo receives confirmation that Vinny has been granted a title fight against Gilbert Dele. Vinny wins the bout via technical knockout, which makes him the WBA World Light Middleweight champion. Some days later, Angelo tells Vinny that he will be fighting Panamanian boxer Roberto Durán. Vinny is pleased, and gets in a car with his friend Jimmy to get some coffee. On the way, they are hit head-on by an oncoming car. Jimmy is hurt, but Vinny suffers a critical neck injury. As he regains consciousness in the hospital, the doctor informs him that he might never walk again, and will certainly never fight again. He offers to better Vinny's chances of walking by performing a spinal fusion. While this would guarantee that he can walk again, it would limit movement in his neck. Thus, boxing would be out of the question. Against his doctor's recommendation, Vinny opts to be fitted with a Halo, a medical device in which a circular metal brace is screwed into the skull in four spots, and propped up with four metal rods. This would allow him to regain movement in his neck, which could allow him to box again. Despite Vinny's optimism, the notion is rejected by Kevin.
Disobeying his doctors' advice, Vinny begins to work out in his basement. He tells Kevin, who agrees to help him. Angelo eventually catches them, and kicks Kevin out of the house.
Six months after the accident, Vinny is ready to have the halo removed. He chooses to endure the pain of having the screws removed without taking any sedatives.
In his comeback match, it is confirmed that Vinny will fight against Durán. The fight is held in Las Vegas, in 1990. In the first six rounds, Vinny is overpowered by Durán. Then suddenly, inspired by his own tenacity, Vinny lands a good punch late in the fight. Vinny eventually wins, via 12-round majority decision (114-114, 115-113, 115-113).
In the final scene, Vinny is interviewed by a journalist. She asks him about the biggest lie he was ever told as a boxer. Vinny pauses, then says the biggest lie is, 'It's not that simple'.