High school senior Ferris Bueller (Matthew Broderick), decides to skip school on a nice spring day by faking an illness to his parents (Lyman Ward and Cindy Pickett), then encourages his girlfriend, Sloane (Mia Sara), and his pessimistic best friend, Cameron (Alan Ruck), to spend the day in Chicago as one of their last flings before they head off to different colleges. Ferris persuades Cameron to let them use his father's convertible 1961 Ferrari 250 GT California, of which only 55 were built, and, according to Cameron, was in pretty bad condition, until his father took three years to restore it to its former glory, which Ferris wants to use, to travel into the city. The rest of the school and many residents learn of Ferris' exaggerated illness and offer donations to help "Save Ferris." Only two people are not convinced by Ferris's deception: his often sarcastic sister Jeanie (Jennifer Grey), outraged at Ferris's ability to defy authority easily, and the school's Dean of Students, Edward Rooney (Jeffrey Jones), who believes Ferris to be truant.
Ferris and his friends arrive downtown and leave the Ferrari with two garage attendants, who drive off in it a short time later to take a joyride. Ferris, Sloane and Cameron enjoy many sights of the city, including taking in a game at Wrigley Field, visiting the Sears Tower, the Art Institute of Chicago, the Chicago Mercantile Exchange and taking part in the Von Steuben Day Parade, with Ferris lip-syncing to "Danke Schoen" and The Beatles' version of "Twist and Shout". Ferris even uses his ploys to pretend he is Abe Froman, the Sausage King of Chicago, to dine at an upscale restaurant, Chez Quis, on Rush Street, while narrowly avoiding his father, who is on his way to lunch with business associates.
Meanwhile, Rooney has gone off-campus to try to find Ferris, first at a local hangout, then traveling to Ferris's home. Rooney attempts to gain entry, but ends up getting stuck in the mud and losing his shoe while being chased by the family's dog. Rooney eventually gains access, but Jeanie comes home, trying to find Ferris and discovers him in the kitchen, mistaking him for a burglar. She kicks him several times, also applying a series of punches to his face, and runs up the stairs to call the police. This forces Rooney to flee the scene, dropping his wallet in the process. When the police show up, they take in Jeanie for prank calling, and while at the police station, she talks to a drug addict (Charlie Sheen), who tells her that she needs to stop worrying so much about Ferris and more about herself. Jeanie becomes increasingly annoyed with the drug addict, but is found kissing him when her mother arrives to pick her up, upset at having to do so.
At the end of the day, Ferris and his friends retrieve the Ferrari, but discover on the way back that hundreds of miles have been added to the odometer, sending Cameron into a panic attack, with Ferris saying, to the audience, "This is where Cameron goes berserk." Cameron goes catatonic, fearing his father's reaction, even trying to drown himself in Ferris's pool, before Ferris saves him. After calming Cameron down, Ferris comes up with a plan to run the car in reverse while running in place at Cameron's father's hillside garage, hoping to reverse the odometer. When they realize this is not working, Cameron unleashes his pent-up anger against his father, damaging the front of the Ferrari, but comes to realize he is long due to stand up to his father and vows to accept the consequences. Cameron calms down and rests himself against the car, but his previous actions have unbalanced it from the jack it was on, the car hits the floor, races in reverse and crashes through the glass wall, landing in a ravine behind the house. Despite Ferris's offer to take the blame, Cameron still plans to 'take it' and admit his actions to his father, feeling that he has let things roll by his whole life and wants to experience what he does.
Ferris walks Sloane home, then quickly races through the backyards of his neighborhood, attempting to beat his parents home. He has several minor run-ins with his parents and Jeanie, each almost leading to the discovery of his absence from bed. When he gets there, he finds Mr. Rooney waiting for him. However, Jeanie, who sped home despite her mother's demands, finds the two, thanks Rooney for driving Ferris back from the hospital, and shows him the wallet he left behind when he broke in earlier, throwing it into a nearby pool. Rooney is attacked by the family's dog and Ferris quickly thanks Jeanie for the diversion, making it into bed just as his parents check on him.
As the credits are rolling, Rooney, in his disheveled state, is invited by the bus driver to catch a ride back to school on a school bus as it drives students home. After the credits are finished, Ferris emerges from the bathroom, speaking directly to the audience, "You're still here? It's over! Go home! Go!" before he turns around and goes into the bathroom again.
