High school senior Ferris Bueller (Matthew Broderick) decides to skip school on a 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 graduate and head off to different colleges. Ferris persuades Cameron to let them use his father's restored 1961 Ferrari 250 GT California to pick up Sloane (as part of their cover) 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". However, only two people are not convinced by Ferris' deception: his sister, Jeanie (Jennifer Grey), outraged at Ferris' ability to defy authority easily, and the school principal, Edward Rooney (Jeffrey Jones), believing Ferris to be truant.
Ferris and his friends arrive downtown and leave the Ferrari with two garage attendants (Richard Edson and Larry Jenkins), who drive off in it a short while later to take a joyride. Ferris, Sloane, and Cameron enjoy the sights, 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 also uses his ploys to pretend he is Abe Froeman, the Sausage King of Chicago, to dine at an upscale restaurant on Rush Street (while narrowly avoiding Ferris's father, who is on his way to lunch with business associates).
Meanwhile, Mr. Rooney has gone off-campus to try to find Ferris, first at a local hangout, then to Ferris's home, where Mr. Rooney attempts to gain entry, but ends up getting stuck in the mud and losing his shoe and wallet while being chased by the dog. Jeanie comes home to look for Ferris, instead discover Mr. Rooney, whom she mistakes for a burglar. She calls the police, forcing Mr. Rooney to flee the scene. When the police show up, they haul Jeanie in for prank calling, and at the police station, she talks to a drug dealer (Charlie Sheen), who tells her that she needs to stop obsessing about her brother and focus about herself. Jeanie's mother shows up to collect her, upset at having to do so.
At the end of the day, Ferris and his friends retrieve the Ferrari, but discover on the way home that hundreds of miles have been added to the odometer, sending Cameron into a panic fearing his abusive father's reaction. After calming Cameron down, Ferris comes up with a plan to run the car in reverse, in place, with its rear wheels jacked up, 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 ground, races in reverse, and crashes through a glass wall, landing in a ravine. Despite Ferris's offer to take the blame, Cameron still plans to admit his actions to his father and take the consequences.
Ferris walks Sloane home, then quickly races through the backyards of his neighborhood, attempting to beat his parents home. When he gets there, he finds Mr. Rooney waiting for him. However, Jeanie, apparently having come to appreciate her brother's craftiness, has sped home despite her mother's demands, and finds the two first. She pretends to scold Ferris for trying to walk home from the hospital while he is so ill, and thanks Mr. Rooney for driving him home, making sure to show Mr. Rooney the wallet he left behind when he broke in earlier. Ferris makes it into bed just as his parents check on him.
As the credits roll, Mr. Rooney in his disheveled state is forced to catch a ride back to school on a school bus as it drives students home. And in the tag at the very end of the credits, Ferris emerges from the bathroom, pleading to the audience directly, "You're still here? It's over! Go home! Go!" before he turns around and reenters the bathroom.