High school senior Ferris Bueller decides to skip school by telling his parents he is sick. He goads his depressive best friend Cameron Frye to join him, and despite Cameron's objections, they take his father's prized 1961 Ferrari 250 GT California Spyder convertible. Sympathy spreads for Ferris's feigned illness, starting the "Save Ferris" campaign, but he cannot fool his suspicious sister Jeanie, nor the school's Dean of Students, Edward Rooney, who believes Ferris to be truant. Throughout the film, he breaks the fourth wall by explaining to the audience his thoughts and techniques.
By phoning the school with a false report of her grandmother's death, Cameron and Ferris get Ferris's girlfriend Sloane Peterson to join them for the day. Ferris, Sloane, and Cameron drive into downtown Chicago, leaving the Ferrari with two garage attendants, who promptly take it on a joyride. The three friends experience a charmed, carefree day in the city, including lunch at a fancy restaurant (where they almost encounter Ferris' dad), a Chicago Cubs game at Wrigley Field (where they are almost spotted on TV by Rooney), and visits to the Sears Tower, the Art Institute of Chicago, and the Chicago Mercantile Exchange. Ferris crashes the annual Von Steuben Day Parade, lip-synching to Wayne Newton's cover of "Danke Schoen" and the Beatles' "Twist and Shout" on the float as the very enthusiastic crowd joins him singing and dancing.
Meanwhile, Rooney tries to break into the Bueller home but he is attacked by the family's dog. Also looking for Ferris, Jeanie returns home, and she mistakes Rooney for an intruder. She attacks him and calls the police. Rooney leaves to chase down his car, which is being towed for parking in front of a fire hydrant. The police arrest Jeanie for filing a false report, and she talks to a juvenile delinquent (Charlie Sheen), who tells her not to worry about Ferris. Jeanie's mother finds her kissing the delinquent when she arrives to pick her up.
At the end of the day, the three friends retrieve the Ferrari, but discover that over a hundred miles have been added to the odometer. Cameron is shocked into self-analysis: he says he has allowed his fear of his father to dominate his life. Back at Cameron's house, the friends jack up the rear wheels of the car and run it in reverse, but it does not remove the miles on the odometer as they expected. Cameron unleashes his pent-up anger against his father, kicking and damaging the front of the Ferrari. He says that now is the time to stand up to his father and vow the consequences that he has done. Leaning on the car, he accidentally knocks it off the jack, and it crashes through the glass wall of the garage, landing in a ravine behind the house. Ferris offers to take the blame, but Cameron insists that he will take it himself.
While walking Sloane home, Ferris realizes he has five minutes to get home before his parents discover him missing. Ferris is nearly spotted by each of his parents, and his sister. He is caught at the back door by Rooney, who tells Ferris to expect another year of high school under his close personal supervision. However, Jeanie has found Rooney's wallet on the kitchen floor, and she blackmails him with this proof that he was the intruder, leaving Rooney to be attacked by the dog once again. Ferris jumps in bed just before his parents check on him, leaving them convinced of his honesty.
During the credits, Rooney hobbles down the street and then hitches a ride on a school bus to the amusement of the students on the bus.
In the post credits scene, Ferris breaks the fourth wall when he tells the audience that the movie is over and they should go home now.