Doug Glatt (Seann William Scott), is a polite, kind-hearted, but dimwitted bouncer at a bar in Massachusetts. Doug feels ostracized from society, especially since his father and brother are both successful physicians. Doug attends a minor league hockey game with his best friend Pat (Jay Baruchel). Pat taunts the visiting team during a fight and one of their players climbs into the stands, calling him a homosexual slur. Doug, whose brother is gay, steps in and easily beats up the opposing player. Soon after, Doug gets a phone call from the coach of his hometown team who offers him a job as an enforcer.
Meanwhile, veteran enforcer and Doug's idol Ross "The Boss" Rhea (Liev Schreiber) is demoted to the minors after serving a 20-game suspension for slashing an opponent in the head from behind. Three years prior, Rhea hit and concussed the highly skilled prospect Xavier Laflamme (Marc-André Grondin), who has had trouble recovering from the incident due to the fear of being hit, resulting in his being stuck in the minors. After earning the nickname "The Thug", Doug was hired by a farm team in Canada where Laflamme plays, the Halifax Highlanders, to protect Laflamme and be his roommate.
The Highlanders experience success with Doug as their enforcer, and he quickly becomes popular among fans and teammates, much to the chagrin of his parents and Laflamme, who loses ice time and the alternate-captaincy to Doug. Doug becomes romantically involved with Eva (Alison Pill), a hockey fan with a penchant for players.
With four games left on their schedule, the Highlanders need two wins to secure a playoff spot. On a road game in Quebec, after an opposing player concusses Laflamme with a heavy hit, Doug savagely beats the player unconscious and is suspended for the next game against Rhea and the St. John's Shamrocks. Doug encounters Rhea at a diner, where Rhea dismisses Doug's claim that he is a hockey player, calling him a goon. Though Rhea acknowledges Doug's physical prowess and gives Doug his respect, Rhea warns him that if they ever meet on the ice, he will "lay [him] the fuck out." The Highlanders, with Doug suspended and Laflamme hospitalized, lose to the Shamrocks.
Doug reaches out to Laflamme, and promises him he will always have his back on the ice. In their next game, the Highlanders lead 1–0 thanks to strong teamwork between Doug and Laflamme. In the final seconds, Doug blocks a slapshot with his face and his ankle is injured in the ensuing scramble. The Highlanders win, but need a win against Rhea and the Shamrocks in their last game for a playoff spot.
After two periods, the Shamrocks are beating the Highlanders 2–0. Rhea and Doug drop the gloves in the third period. Doug is knocked down first, but Rhea calls off the linesmen and allows him to get back up. Doug manages to break Rhea's nose, but breaks his previously injured ankle in the process. Doug manages to stand back up and knocks out Rhea with a vicious left hook. Eva and his teammates help a seriously injured Doug off the ice and Laflamme, inspired by Doug's efforts and Rhea's defeat, scores a natural hat trick, giving the Highlanders a 3–2 lead. As the game enters its final minute, the final scene has Eva comforting Doug in the locker room as he comments, "I think I nailed him."Seann William Scott as Doug "The Thug" Glatt
Liev Schreiber as Ross "The Boss" Rhea
Alison Pill as Eva
Jay Baruchel as Pat
Marc-André Grondin as Xavier Laflamme
Eugene Levy as Dr. Glatt
David Paetkau as Ira Glatt
Kim Coates as Coach Ronnie Hortense
Richard Clarkin as Gord Ogilvey
Jonathan Cherry as Goalie Marco "Belchie" Belchior
Ricky Mabe as John Stevenson
Georges Laraque as Huntington
Curt Keilback as Rod McCaudry
A red-band trailer for the film was released on IGN.
In Toronto and Montreal, prior to its premiere, posters for the film were removed from city bus shelters after several complaints from the public due to Baruchel making a "sexually suggestive gesture with his tongue and fingers."
The review aggregator Rotten Tomatoes reports 82% positive reviews from 104 critics. Metacritic gives the film a score of 64 out of 100 based on reviews from 24 critics.
Stephen Holden, writing for The New York Times gave a positive review that credits all the major performances. Goon was nominated for three awards at the 1st Canadian Screen Awards: Michael Dowse for Achievement In Direction, Jay Baruchel and Evan Goldberg for Best Adapted Screenplay, and Jay Baruchel and Kim Coates, both for Performance By An Actor In A Supporting Role.
The timing of the film’s release was considered controversial by some as the previous summer featured the deaths of three NHL enforcers – Derek Boogaard, Rick Rypien and Wade Belak – all three of whom suffered from depression and head trauma that are believed to be factors in their deaths.
Baruchel wrote a sequel with Jesse Chabot. Michael Dowse was stated to return to direct but it was Baruchel who directed the film, making it his directorial debut. Evan Goldberg produced the sequel. The title of the film is Goon: Last of the Enforcers.
In a interview Baruchel expressed interest in a third movie, “I don’'t want to get into trouble, and I'm not saying there's going to be a Goon 3," Baruchel says, "but there's more than one way to skin a cat. We're not done in this universe yet."