In 2002 Los Angeles, a young Adonis "Donnie" Creed sneaks out with his best friend, Damian "Diamond Dame" Anderson, a Golden Gloves champion, to witness a thrilling underground boxing match. After witnessing Dame's victory, he shares his dreams of turning professional and capturing a world championship. However, an impulsive moment leads Donnie to assault a man named Leon during a liquor store stop.
Fast forward to 2018, Donnie faces off against the formidable "Pretty" Ricky Conlan in a rematch shortly after Ricky's release from prison, emerging victorious. Choosing a life outside the ring, Donnie retires to focus on his wife, Bianca, and their daughter, Amara. Three years down the line, Donnie manages the Delphi Boxing Academy alongside his coach, Tony "Little Duke" Burton, while promoting his protégé, world champion Felix "El Guerrero" Chavez, gearing up for an intense bout against Viktor Drago. Meanwhile, Bianca, grappling with her hearing difficulties, transitions from performing to a successful career as a producer. Together, they also care for Donnie's adoptive mother, Mary Anne Creed, whose health is declining. Amara aspires to box like her father, which leads her into some trouble at school.
The plot thickens when Dame is released from prison and reaches out to Donnie, expressing his ambitions to reignite his boxing career. Hesitantly, Donnie invites Dame to spar with Chavez at the gym, but Dame's aggressive antics stir up disapproval. Later, during a visit to Donnie's home, Dame reminisces about their shared past in a group home—a secret Donnie has kept from Bianca. Privately, Dame expresses his desire for a shot at the title against Chavez, leaning on the evidence of Donnie's miraculous rise to fame, which Donnie refuses.
At a celebration for Bianca’s record label, Dame ominously brings up Leon before another twist occurs: Drago is attacked by an unknown assailant, casting uncertainty on his upcoming fight with Chavez. In a bold move, Donnie proposes Dame as a contender to Chavez, promoting an underdog confrontation much like how his father once faced Rocky. The fight culminates in Dame defeating Chavez and seizing the undisputed heavyweight championship.
After the match, Donnie is uneasy as he pays a visit to Mary Anne, who reveals letters written by Dame while incarcerated—letters that she withheld from Donnie due to her belief that Dame was a bad influence. Among them, one contains a photo of Dame with an inmate who Donnie identifies as the man responsible for assaulting Drago. Confronted with the truth, Donnie realizes Dame orchestrated the attack and has meticulously planned to take vengeance for the perceived betrayal during their youth. This revelation plunges Donnie into a well of guilt, especially as Dame publicly defames him, branding him a fraud.
Tragedy strikes when Mary Anne suffers a stroke and passes away. After her funeral, Donnie confides in Bianca about his past: Leon was the abusive figure in the group home that both he and Dame lived in before Donnie's adoption. The memory of attacking Leon set off a chain of events that led to Dame's consequent arrest, a memory that haunts Donnie, prompting him to block out communications with Dame due to his shame.
With Dame’s relentless defamation intensifying, Donnie realizes he must take action. He appears on First Take where Dame provocatively calls in, challenging Donnie’s character. Ultimately, Donnie decides to make a comeback, throwing down the gauntlet for a championship rematch—one that Dame eagerly accepts.
The stage is set for the "Battle of Los Angeles" at Dodger Stadium. As the duo goes toe-to-toe, Donnie finds himself grappling in a fiercely contested bout. In the final round, empowered by Duke's counsel to confront his fears and guilt, Donnie exploits Dame’s waning energy, clinching a decisive knockout that earns him both the match and the championship.
In the aftermath, Donnie and Dame come to an understanding, both acknowledging that their paths were influenced by their shared past. As the champion embraces his family, he imagines a playful boxing match with Amara in the empty stadium, signifying warmth and reconciliation in the wake of their tumultuous journeys.
