During a banquet, legendary football coach Pop Warner Charles Bickford rises and gives a speech praising Jim Thorpe, which leads to a flashback.
Young Jim Thorpe runs all the way home before his first day at an Indian reservation school, but his father talks him into going back, telling him that he wants his son to make something of himself. Years later, a now-adult Jim arrives on the campus of Carlisle School to continue his education. He likes his roommates at the boarding school well enough, fast-talking Ed Guyac and the huge Little Boy Who Walk Like Bear, but nearly gets into a fight with upperclassman and football star Peter Allendine.
When the academic pressure becomes too much for him, Jim goes for a long run, during which he outraces some practicing track athletes. Witnessing this, Pop Warner talks Jim into joining the track team. Jim is so talented, versatile, and quick to learn that, at the next meet, Pop's team consists of just him (competing in all but the distance running events) and one other man. Jim by himself beats the other team. After a while, the newspapers are reporting his impressive feats.
Jim is attracted to Margaret Miller Phyllis Thaxter, but has to compete for her affections with Peter Allendine. Seeing that football is more prestigious than track, he applies to join the football team. Pop, worried about losing most of his track team with a single injury, turns him down, then reluctantly gives in. However, he keeps Jim on the sideline. Finally, he lets Jim play in a game against Harvard, but only to kick the ball away. The first time, Jim is tackled for a loss before he can kick. The second time, he again has trouble catching the ball; about to be tackled, he starts running and scores a touchdown. Soon, he is a celebrated football star.
Jim tells Pop that he has finally figured out what he wants to do with his life: coach. Later, Pop tells him that scouts from a school looking for a coach will be in the crowd watching a showdown between Carlisle and an undefeated University of Pennsylvania juggernaut headed by another All-American, Tom Ashenbrunner. The teams end up in a 13–13 tie after Jim kicks a seemingly impossible field goal in the dying seconds. However, the job goes to the white Ashenbrunner. Jim suspects it is because he is an Indian.
By this time, he and Margaret are dating. Eventually, he tells he wants to marry her, in part because they belong together, as they are both Indians. When Margaret does not return for the new semester, Jim becomes despondent, particularly after he learns that Margaret is white. Pop arranges for Margaret to get a job as a nurse at the school, and steers Jim to her. They reconcile and get married.
Jim decides to become so famous someone will have to hire him as a coach. He enters the 1912 Olympics and wins both the pentathlon and the decathlon. However, when it is discovered that he was paid a pittance to play baseball one summer, he is disqualified and stripped of his medals and trophies because he is not an amateur.
Embittered, Jim turns to professional baseball and football to make a living. He and Margaret have a son, on whom he dotes. He envisions Jim Thorpe Jr. following in his footsteps and recapturing the glory stolen from him. However, the boy dies while Jim is away in Chicago with the Canton Bulldogs, sending him into a downward spiral. Eventually, Margaret leaves him.
Finally, Pop tracks him down, working as a lowly announcer at a dance marathon. Pop offers him a ticket to the opening of the 1932 Olympics, but Jim tears it up. Later, however, he tapes it back together and attends the ceremony. He reconciles with Pop and his resentment dissolves.
One day, he drives over a football that has gotten away from a group of kids. He buys a new one and presents it to the despondent bunch. Watching them play, he starts giving them pointers; they ask him to become their coach, lifting his spirits.
The film then returns to the banquet. Jim, who is in attendance, is inducted into Oklahoma's Hall of Fame.
