After winning his first Tour Championship in 1996, Happy Gilmore (Adam Sandler) has a successful golf career, winning five more championships. He also has five children with his wife Virginia Venit (Julie Bowen). He launches his own golf video game. Happy tries to teach Golf to his kids, but their hockey instincts are way stronger, and they end up beating the other kids on the Golf Course.
After accidentally killing Virginia in 2014 when one of his drives hits her in the head, Happy feels devastated and quits golf out of guilt. Happy loses all of his money and is behind on all of his payments. He soon becomes an alcoholic and loses everything after a repossession worker sues him for instigating a brawl when mistaking the worker for a car thief.
Eleven years later, Happy works at a supermarket and lives with his only daughter and youngest child Vienna (Sunny Sandler), while his four sons Gordie (Maxwell Jacob Friedman), Wayne (Ethan Cutkosky), Bobby (Philip Fine Schneider), and Terry (Conor Sherry) have all moved out and are working to support their father and sister.
Vienna wants to pursue dancing, and her dance teacher recommends enrolling in a four-year ballet school in Paris, which costs $75,000 yearly. The school only has 4 open slots each year and they have kept one slot for Vienna this year. Frank Manatee (Benny Safdie), CEO of Maxi Energy Drink and the upcoming golf league Maxi Golf, later approaches Happy and wants him to be the league's star. Happy refuses but resumes playing golf with encouragement from John Daly, wanting to win enough money to put Vienna through ballet school.
Happy starts at the bottom and tries to complete 18 holes at a local municipal course. However, he had lost all his skill and missed more shots than he hits. During his first game since Virginia died, Happy gets heavily drunk and crashes his golf cart, which gets him fired from his job and in legal trouble.
A jury agrees to remove all charges if he completes an alcohol treatment program and refrains from any physical altercations. This treatment program's leader turns out to be Hal L. (Ben Stiller), the abusive leader of a support group for alcoholics and the caretaker who abused Happy's grandmother.
Having been in psychiatric care since losing to Happy at the 1996 Tour Championship, Shooter McGavin's (Christopher McDonald) case come up for a parole hearing. All goes well until the committee wants to know what Shooter would do if he came across Happy wearing a Gold jacket. Shooter loses all his composure and goes berserk and is remanded back into custody of the mental hospital.
Vienna and John advise Happy to practice seriously and to join the next Tour Championship, which he does. Even if he finishes 30th in the Tour Championship, Happy would make a $100,000 in prize money. With gradual practice and support from his friends, Happy gets better at Golf, even though he is 58 years old now.
Happy meets old companions, including Doug Thompson (Dennis Dugan), president of the Tour, who worries about Maxi Golf rising fast. Frank had managed to launch his league without Happy, but he knew that having Happy as part of the league would definitely take it to the next level. Frank claimed that his league had the better golfers and that the action was faster than in the traditional golf tournaments.
After Happy suggests having a competition between the two leagues, Doug proposes a match with the five best players from each league competing against each other. Happy, with help from his new caddie Oscar Mejias (Bad Bunny), plays well at the Tour Championship in the first three rounds, but collapses in the fourth round on Mother's Day, seeing visions of Virginia on the field before getting drunk, finishing sixth. The winner, Billy Jenkins (Haley Joel Osment), a young pro-golfer with a powerful swing similar to Happy's, admits to being in Maxi Golf, having participated in the Tour Championship as a taunt, vacating his place on the team and enabling Happy to join. Happy won $496,000 from his 6th place at the Tournament, but the organizers fined Happy $500,000 for his drunken discourse during the 4th round.
Shooter is granted a release by Frank. He explains to Shooter that all players on Maxi Golf, including Billy, have their Iliolumbar ligament severed, increasing their driving distance, and asks him to join as their captain. Disgusted with this and how much Frank's "extreme" version of golf strays from the traditional game, Shooter escapes. Frank had 7 hole course and shot clocks to speed the game up.
Having heard about Virginia's death, Shooter visits her grave and briefly fights Happy there before they call a truce. Vienna says that even if she had the money she would not go to Paris unless Happy got a hold of himself and quit drinking. Happy later meets Slim Peterson (Lavell Crawford), whose father Chubbs Peterson had mentored Happy in 1996, and Slim joins Shooter in coaching Happy, Rory McIlroy, Bryson DeChambeau, Brooks Koepka and Scottie Scheffler to face Maxi Golf.
Frank meets Happy before the face-off and offers him 10% of the company to join the league, but Happy refuses.
During the match-up, Scottie gets disqualified in the first round for punching his opponent. Although the field is heavily designed to advantage Maxi Golf, as all their golfers are long drivers, the traditional golfers manage to make it 2-2, with the help of Shooter, who replaces Brooks after he gets injured. Happy and Billy then face off in a tie-breaker.
Happy has a chance to putt for victory, but Frank alters the green to make it impossible to putt. He then makes a deal with Happy: if Happy misses the putt, Happy must join Maxi Golf. Otherwise, Frank must discontinue Maxi Golf, buy Happy's house back, pay for Vienna's ballet school, give Happy his new electric car, and open a new Italian restaurant for Oscar. With help from the latter-most, Happy sinks the putt and wins.
When Happy celebrates his three-month sobriety, Hal is exposed as a con artist and gets arrested. Maxi Energy Drink is discontinued after being revealed to cause significant oral health issues, leaving Frank in ruin and in hiding. Happy later accompanies his kids at an airport as they fly off to Paris, promising to join them after completing the British Open.
