In an upscale New York City mansion, wealthy, popular and intelligent teenager Kathryn Merteuil discusses her private school with Mrs. Caldwell and her daughter, Cecile, who will be starting as a Freshman at the school soon. Kathryn promises Mrs. Caldwell that she will look out for the sheltered, naïve Cecile. When Kathryn's stepbrother Sebastian Valmont enters the room, Mrs. Caldwell reacts to him coldly and leaves with Cecile.
Kathryn tells Sebastian that she intends to use Cecile to take revenge on her ex-boyfriend Court Reynolds, who dumped her for Cecile. Kathryn enlists Sebastian, a notorious womanizer, to seduce Cecile, thereby ruining her in Court's eyes. Sebastian refuses because he is planning to seduce Annette Hargrove, the virgin daughter of the new Headmaster at their school, who has written an essay which was published by a magazine in support of chastity until marriage. After some negotiation, they agree on a wager: if Sebastian fails to seduce Annette, Kathryn gets Sebastian's vintage Jaguar XK140; if he succeeds, Kathryn will have sex with him.
Sebastian's first attempt to seduce Annette fails, as she is apparently already aware of his reputation. Sebastian initially suspects Greg, Annette's friend from Kansas who is a popular football player and closeted homosexual. Sebastian convinces Greg to put in a good word about him to Annette, blackmailing him with a photo of him and Sebastian's openly gay friend in bed. Sebastian also finds out that Mrs. Caldwell was the one who warned Annette about Sebastian. Sebastian finally agrees to corrupt Cecile as revenge. Meanwhile, Cecile confides in Kathryn about her romance with her music teacher, Ronald Clifford. Kathryn reveals this to Mrs. Caldwell, who orders Cecile to end the relationship, but only because Ronald is black. Sebastian lures Cecile to his house by claiming he has a letter to her from Ronald. He then gets Cecile drunk and blackmails her into allowing him to perform oral sex on her. The next day, Cecile confides in Kathryn, who advises her to be as promiscuous as possible to learn how to please Ronald.
Sebastian begins to truly fall in love with Annette, who returns his feelings but is still hesitant. Sebastian calls her a hypocrite for resisting the chance for true love despite claiming that she was waiting for it. Annette finally relents, but Sebastian, confused about his own feelings, now refuses her. Annette flees to the estate of her friend's parents. Sebastian finds her and professes his feelings, and they make love.
Kathryn offers herself to Sebastian after he wins the 'bet', but he rejects her, now only wanting Annette. Sebastian informs Kathryn that he was planning to tell Annette the truth, but a jealous and enraged Kathryn warns him that doing so will destroy both his and Annette's reputations. Sebastian lies to Annette, claiming that she was just a conquest and that he has no real feelings for her. Devastated, Annette tells him to leave. Sebastian informs Kathryn that he has broken up with Annette and now wants his reward for winning the bet. Kathryn reveals that he, not Annette, was the true target of her scheme and that she manipulated him into abandoning Annette for her own amusement. She then dismisses him, telling him that she doesn't sleep with "losers".
Sebastian tries to contact Annette to confess the truth and beg for a second chance, but she refuses to see him. He gives her his journal, in which he has detailed Kathryn's manipulative schemes, their bet, and his true feelings for Annette. Seeking revenge, Kathryn calls Ronald, claiming that Sebastian hurt her and slept with Cecile. Ronald violently confronts Sebastian, and the ensuing fight migrates to the middle of the street. Annette tries to intervene but is thrown into traffic. Sebastian pushes her to safety but ends up getting hit by a taxi. Sebastian and Annette confess their love for each other before he dies.
At Sebastian's funeral, Kathryn delivers a eulogy, which people start leaving midway through. Kathryn rushes outside to find Cecile handing out copies of Sebastian's journal. As the details of her manipulations and drug abuse are made public, Kathryn's reputation is finally destroyed. It is implied that the disapproving headmaster will expel her from the school, especially after finding cocaine hidden in the cross of her rosary. In the final scene, Annette drives away in Sebastian's car with his journal at her side, recalling their fondest moments together.
Sarah Michelle Gellar as Kathryn Merteuil, based on the Marquise de Merteuil
Ryan Phillippe as Sebastian Valmont, based on the Vicomte de Valmont
Reese Witherspoon as Annette Hargrove, based on Madame de Tourvel
Selma Blair as Cecile Caldwell, based on Cécile Volanges
Louise Fletcher as Helen Rosemond, based on Madame de Rosemonde
Joshua Jackson as Blaine Tuttle
Eric Mabius as Greg McConnell
Sean Patrick Thomas as Ronald Clifford, based on the Chevalier Danceny
Swoosie Kurtz as Dr. Regina Greenbaum (Kurtz portrayed Madame de Volanges in the 1988 film version of Dangerous Liaisons)
Christine Baranski as Bunny Caldwell, based on Madame de Volanges
Alaina Reed Hall as Nurse
Deborah Offner as Mrs. Michalak
Tara Reid as Marci Greenbaum
Hiep Thi Le as Mai-Lee
Herta Ware as Mrs. Sugarman
Drew Snyder as Headmaster Hargrove
Charlie O'Connell as Court Reynolds, based on the Comte de Gercourt
Fred Norris as Meter Maid