In the town of Urbania, Ohio, Kevin O'Shea is a Heisman Trophy winner and local sports hero who coaches the Pee-Wee Cowboys. He enjoys the spotlight but faces a setback when his niece Becky 'Icebox' O'Shea is cut from the team simply for being a girl. Her friends Rashid Hanon, Tad Simpson, and Rudy Zolteck are also cut. Becky convinces her dad Danny O'Shea, Kevin's younger brother, to coach a rival pee-wee squad in a bid to show Urbania that another O'Shea can win.
Danny accepts to prove it, and with local support the brothers stage a playoff to decide which team will represent Urbania. Becky and other overlooked kids form the Little Giants. Junior Floyd is one of their standout players, the son of Patty Floyd.
Two old-timers, Orville and Wilbur, stir the rivalry by telling tales of the town's past and fueling the competition. Danny recruits Spike Hammersmith by posing as the famous "Coach O'Shea," but Spike refuses to play on a team with a girl. The deception is revealed, and he switches to Kevin's side. Kevin also encourages his daughter Debbie to become a cheerleader, suggesting a quarterback dating the cheerleaders may be more appealing, prompting Becky to consider cheerleading over playing, and she briefly quits.
A bus arrives with NFL stars who visit the kids, offering guidance and hope, rejuvenating their belief in themselves.
On game day, a playful bet is laid out: if Danny wins, he gets Kevin's Chevrolet dealership; if Kevin wins, he gets Danny's gas station. With a 21-point deficit at halftime, Danny's motivational speech helps the Giants remember past milestones and their ability to beat the Cowboys at least once.
During the game, Mike Hammersmith orders Spike to target Junior after the whistle, injuring him. Kevin confronts the actions, warning Spike that such behavior won't be tolerated. Becky, furious, drops her pompoms and suits up, making an immediate impact by forcing a fumble on Spike. In the final seconds, with the score tied 21-21, Becky helps the Giants withstand a late drive at the goal line. The offense then runs a daring play, conceived by Nubie, the Little Giants' assistant coach, called The Annexation of Puerto Rico, featuring a series of handoffs that ends with Jake Berman scoring a 99-yard game-winning touchdown after passes from Junior.
After the win, Danny proposes a merger of the two town teams so Urbania can benefit from both coaches, and Patty Floyd's relationship with Danny rekindles. The town changes the water tower inscription from "Home of Kevin O'Shea" to "Home of The O'Shea Brothers," honoring an old promise from their childhood.
