While their mother is away, high school-aged twin siblings David and Jennifer fight over the television, breaking the remote control. A TV repairman arrives and, impressed by David's knowledge and love of Pleasantville, a black-and-white 1950s sitcom about the idyllic Parker family, gives him an unusual remote control before departing. When they use it, David and Jennifer are transported into the Parkers' house, in Pleasantville's black-and-white world. George and Betty Parker believe them to be their children, Bud and Mary Sue. Communicating through the Parkers' television, David tries to reason with the repairman, who is offended that they want to come home, thinking they should be lucky to live in Pleasantville.
There, fire does not exist, and firefighters merely rescue cats from trees, and everyone is unaware that anything exists outside of Pleasantville, as all roads circle back into it. David tells Jennifer they must play the show's characters and not disrupt Pleasantville, but she rebelliously goes on a date with Mary Sue's boyfriend, Skip Martin, the most popular boy in school. She has sex with Skip, who is shocked by the experience, which leads to the first bursts of color appearing in town.
Bill Johnson, owner of the malt shop where Bud works, experiences an existential crisis after realizing the repetitive nature of his life. David tries to help him break out of his routine and notices an attraction between Bill and Betty.
As Jennifer influences other teenagers, parts of Pleasantville become colorized, including some of the residents. Books in the library, previously blank, begin to fill with words after David and Jennifer summarize the plot to their classmates. When Jennifer gives a curious Betty an explanation about sex and tells her how to masturbate, Betty has an orgasm that results in her colorization and a fire in a tree outside.
Other foreign concepts, such as rain, begin to appear. David shows Bill a book of modern art, which inspires him to begin painting and to pursue a romance with Betty. Jennifer loses interest in sex and partying and becomes colorized after finding passion in literature. David pursues a romance with Margaret but is confused and disappointed to find he is still black and white.
Betty leaves George to be with Bill, bewildering him. The town leaders, including the mayor, Big Bob, and others who remain black and white are suspicious of all of these changes and begin to discriminate against the "colored" people, considering them a threat to Pleasantville's values.
A riot is ignited by Bill's nude painting of Betty on the window of his malt shop. The shop is destroyed, books are burned and colored people are harassed in the street. David defends Betty from a gang of teenage boys. Punching one of them, David scares the rest away, demonstrating newfound courage that turns him colored.
The town council bans colored citizens from public venues, closes Lover's Lane, outlaws reading, rock music and using colorful paint. In protest, David and Bill paint a colorful mural outside the soda fountain depicting the beauty of love, sex, rain, music and literature. They are arrested and brought to trial in front of the entire town. David confronts George about losing Betty, persuading him to admit he does not just miss the cooking and the cleaning. George becomes colorized and the rest of the town, except for Big Bob, become colorized as well. When David drives him to fury over the suggestion that one day there could be a world where women go off to work and men stay home and cook, Big Bob becomes colored and flees in shame.
The town celebrates their victory, and color televisions start being sold. They broadcast new programs and footage of other countries. The town's roads also start leading to other cities. With Pleasantville changed, Jennifer chooses to continue her new life in the TV world. Bidding farewell to her, Margaret and Betty, David uses the remote control to return to the real world, where only an hour has passed since his disappearance. He comforts his mother, who had left to meet a man only to get cold feet, and assures her that nothing has to be perfect. In Pleasantville, citizens enjoy their lives, and Jennifer attends college.
