Andy "Champ" Purcell (Beery) is a former heavyweight boxing champion who lost his title due to alcoholism and now is a washed-up fighter eking out a meager existence in Tijuana. The only bright spot in his life is his precocious, adorable eight-year-old son Dink (Cooper). In addition to being an alcoholic, Andy has a gambling habit, and one night he has enough luck playing dice to win a bunch of money. He gets Dink a racehorse. Andy and Dink take the horse to a racetrack, where they meet a fancy rich lady and her rich husband. The fancy lady turns out to be Dink's long-lost mother Linda (Irene Rich), who is currently living in considerably more comfortable circumstances than her impoverished ex-husband. Soon enough, Dink's mother decides that she wants him back.
Even in 1931, The Champ was attacked for its melodrama and sentimentality, but the strong performances of Cooper and Beery help sell the story. The Champ was nominated for four Academy Awards and won two, including Best Actor for Beery. (Beery actually received one fewer vote than Fredric March did for Dr. Jekyll and Mr. Hyde (1931), but under an Academy rule of the day any result decided by less than three votes was considered a tie, so both Beery and March received awards.)
- Adorably Precocious Child: Dink seems to look after his bumbling, drunken dad better than Andy looks after Dink. He has to badger his dad to train instead of drinking so much.
- The Alcoholic: Apparently Andy's drinking is what ruined both his boxing career and his marriage sometime in the backstory. He ruins a meeting with promoters by showing up drunk.
- As You Know: Some helpful exposition between Andy and Linda's husband Tony about how Andy's drinking wrecked his life.
- Big Game: Or a big fight, as Andy gets a big comeback fight against the Mexican heavyweight champion.
- Break His Heart to Save Him: When Andy is in jail and has to tell Dink he's sending him to live with his mother. Dink of course, refuses. Andy resorts to telling Dink he doesn't want him anymore and that he's sick of feeding him.
- Casualty in the Ring: Andy collapses and dies after winning his fight.
- Downer Ending: Hoo boy. Andy collapses on the way to the locker room after the fight. He then dies, as Dink cries his eyes out at his side.
- Gender Flip: The whole movie can be seen as a Gender Flip of the typical melodrama plot in which a spurned woman is left to raise her child alone, only to have the Glorified Sperm Donor swoop in years later demanding parental rights.
- Glorified Sperm Donor: Glorified Egg Donor, as Linda, who apparently was content to run off with her new rich husband several years ago, now wants to take Dink away from Andy.
- Hope Spot: Andy, who was getting a beatdown—he is knocked down three times in one round, which would result in a TKO loss in a lot of boxing organizations—comes back and wins the fight. Then he shows Dink the horse, which he has bought back for Dink after gambling him away earlier in the movie. Life is great! Until it isn't.
- Luke, I Am Your Father: Dink was under the impression that his mother was dead, until she reveals herself to him.
- Missing Mom: It seems she ran off and married a rich guy.
- Please Wake Up: The 1979 remake's climatic scene is perhaps one of the trope codifiers: Champ (renamed Billy Flynn) collapses from exhaustion in the locker room and dies shortly afterward winning his final match, and his son, T.J., begging for the worst not to be true but completely collapsing into tears when it is clear that his father has died in front of him.
- Soundtrack Lullaby: At the end of the film, as Dink sobs into his mother's arms following Champ's death, "Brahms' Lullaby" starts to play over the end title.
- Truth in Television: As the Davey Moore case showed, it's not unthinkable for a boxer to leave a contest seemingly all right, only to rapidly deteriorate and die afterwards.