Brendon Conlon (Joel Edgerton) is a well-liked high school physics teacher who finds himself facing the foreclosure of his home due to poor financial decisions. Fearing that he will not be able to provide for his wife and children, he returns to the ring to earn some extra money. Once the word that he has been fighting spreads throughout his school, he is placed on suspension without pay, and he is forced to fight full-time just to have a shot to keep his home. He begins training with Frank Campana (Frank Grillo), who is training another fighter to compete in Sparta. When the fighter is injured Brendon begs Frank to let him take his place. Frank agrees, and the two begin to train feverishly to get Brendon ready to fight.
Tommy Riordan (Tom Hardy) is a former Marine who has now returned home to live with his father. He joins a gym where one of the top MMA fighters in the world trains. When a sparring partner doesn't show up, Tommy steps in and brutally knocks the fighter out. Recorded footage of the fight is placed online and then goes viral, making Tommy an overnight sensation. Tommy then asks Paddy to help him train for Sparta. Tommy's reasons for fighting are unknown, but he is driven by something much greater than his anger.
Warrior is a film about family, survival, and ultimately, forgiveness.