In May 1962, 16-year-old overweight high school student Tracy Turnblad lives in Baltimore along with her shy best friend Penny Pingleton. Both frequently watch The Corny Collins Show, a local teen dance television show broadcast live on the WYZT station. Several of the dancers on the show, among them lead dancers Amber von Tussle and her boyfriend Link Larkin, attend Tracy and Penny's high school. Amber's mother Velma, the station's manager, ensures that her daughter is prominently featured and, as Corny Collins and the main dancers are white, only allows African-American dancers to appear on the monthly "Negro Day", hosted by local R&B disc jockey "Motormouth" Maybelle Stubbs.
When Corny announces that Brenda, a dancer on the show, will be taking a nine-month leave of absence, Tracy becomes ecstatic, especially when Link announces auditions for a replacement to be held at the WYZT studio the next day. At the audition, Velma rejects her for both being overweight and supporting integration. Given detention for skipping class, Tracy discovers the "Negro Day" kids practicing in the detention room and befriends Motormouth Maybelle's son, Seaweed, who teaches her several dance moves. While leaving detention, she inadvertently meets Link, dreaming of life with him. At a record hop, her new moves garner Corny's attention, and he chooses her to join the cast.
Tracy quickly becomes one of Corny's most popular performers, affecting Amber's chances of winning the show's annual "Miss Teenage Hairspray" pageant the following month and her relationship with Link, who grows fonder of Tracy. When Mr. Pinky enlists her as the spokesgirl for his Hefty Hideaway boutique, she persuades her agoraphobic mother, Edna, to accompany her there as her agent, where both receive makeovers, sharply boosting Edna's confidence.
Tracy introduces Seaweed to Penny, and the two become smitten. Later, Seaweed and his younger sister Little Inez take Tracy, Penny, and Link to a party at Maybelle's store. Amber, upset over losing Link to Tracy, follows her mother's advice and anonymously calls Edna to reveal her daughter's current whereabouts, which causes Edna to rush to the store and attempt to take her home immediately, but Maybelle convinces her to stay and take pride in herself. After Maybelle sadly informs everyone that Velma has cancelled Negro Day, Tracy suggests they march for integration. Link, unwilling to endanger his career, sincerely apologizes to Tracy, upsetting her by explaining that he is scheduled to sing in front of talent scouts at the pageant. Edna returns to her husband Wilbur's shop, but Velma gets there first, and tries to seduce him. Though he remains impervious to Velma's advances, Edna arrives to see Velma forcing him into a compromising position and furiously storms out. After accusing Wilbur of infidelity and changing the locks, Edna, out of hatred for Velma, forbids Tracy to be on the show, but changes her mind after reconciling with Wilbur.
The next morning, Tracy sneaks out of the house to join the protest, which is halted by a police roadblock. The protesters engage in a brawl, while Tracy runs to the Pingletons' home, where Penny hides her in a fallout shelter. However, Penny's mother Prudy reports Tracy to the police and ties her daughter to her bed for "harboring a fugitive". Having been bailed out by Wilbur, Seaweed and his friends help Tracy and Penny escape. Link visits Tracy's house to find her, realizing that he loves her. Seaweed and Penny also acknowledge their love during the escape.
With the pageant underway, Velma assigns police officers to guard the WYZT studio to prevent Tracy from entering and rigs the pageant tallies to guarantee Amber's victory. Penny arrives at the pageant with Edna, while Wilbur, Seaweed, and the Negro Day kids help Tracy infiltrate the studio. Link breaks away from Amber to dance with Tracy; later, he pulls Little Inez to the stage to dance in the pageant.
Amber's attempt to re-claim her championship crown fails. Little Inez wins the pageant after a late surge of support, successfully integrating the program. Edna mans a camera to film Velma revealing her rigging scheme to Amber, resulting in Velma's dismissal. The set turns into a celebration as Tracy and Link cement their love by kissing each other.
John Travolta as Edna Turnblad
Nikki Blonsky as Tracy Turnblad
Michelle Pfeiffer as Velma Von Tussle
Amanda Bynes as Penny Lou Pingleton
Christopher Walken as Wilbur Turnblad
Queen Latifah as "Motormouth" Maybelle Stubbs
James Marsden as Corny Collins
Brittany Snow as Amber Von Tussle
Zac Efron as Link Larkin
Elijah Kelley as Seaweed J. Stubbs
Allison Janney as Prudence "Prudy" Pingleton
Paul Dooley as Harriman F. Spritzer
Jayne Eastwood as Miss Wimsey
Jerry Stiller as Mr. Pinky
Taylor Parks as Little Inez Stubbs
George King as Mr. Flak
based on the 2002 Broadway musical of the same name, which in turn was based on John Waters's 1988 comedy film of the same name