00:00 - Charlie Schumaker / Richard Jeni
00:10 - Niko / Orestes Matacena
00:20 - Freeze / Reg E. Cathey
00:30 - Dr. Arthur Neuman / Ben Stein
00:40 - Peggy Brandt / Amy Yasbeck
00:50 - Lt. Mitch Kellaway / Peter Riegert
01:00 - Dorian / Peter Greene
01:10 - Tina Carlyle / Cameron Diaz
01:20 - Stanley Ipkiss / Jim Carrey

In Edge City, insecure bank clerk Stanley Ipkiss is frequently ridiculed by everyone except for his co-worker and best friend, Charlie Schumaker. Meanwhile, gangster Dorian Tyrell, who owns the Coco Bongo nightclub, plots to overthrow his superior, Niko. One day, Tyrell sends his dazzling singer-girlfriend, Tina Carlyle, into the bank to record its layout for an upcoming robbery. Stanley is attracted to Tina and she seemingly reciprocates.

After being denied entrance to the Coco Bongo to watch Tina perform, Stanley's faulty loaner car breaks down during his drive home. While looking over the harbor bridge in despair, he tries rescuing a humanoid figure in the waters but finds it to be a pile of garbage concealing a wooden mask. Upon returning to his apartment and donning the mask, he transforms into a green-faced, zoot-suited trickster known as "the Mask", who can cartoonishly alter himself and his surroundings at will. With newfound confidence, Stanley indulges in a comical rampage through the city, humiliating several of his tormentors, including his temperamental landlady, Agnes Peenman, and the mechanics who gave him the faulty car.

The next morning, Stanley encounters detective Lieutenant Mitch Kellaway and newspaper reporter Peggy Brandt, both of whom are investigating the Mask's activity. To obtain the funds necessary to attend Tina's performance, Stanley dons the mask and raids the bank, inadvertently foiling Tyrell's robbery. At the Coco Bongo, Stanley dances exuberantly with Tina, whom he ends up kissing. Shortly after, Tyrell confronts him for disrupting the robbery and Stanley flees, leaving behind a scrap of cloth from his suit, which reverts into a piece of his pajamas. After arresting Tyrell and his henchman, Kellaway finds the piece of cloth and suspects Stanley's involvement.

Later, Stanley consults Doctor Arthur Neuman, a psychiatrist who has recently published a book on masks, and deduces that the mask may be a creation of Loki, the Norse god of mischief, and its powers are only active at night. Though Neuman believes it is mythology, he concludes that the Mask's personality is based on Stanley's repressed desires. That night, Stanley meets Tina at a local park as the Mask, until they are interrupted by Kellaway, who attempts to capture him. Stanley flees with Peggy after he distracts the police with a mass performance of the titular song from Cuban Pete; she then reluctantly betrays him to Tyrell for a $50,000 bounty. Tyrell dons the mask, becoming a bulky and malevolent green-faced being. Tyrell's henchmen force Stanley to reveal the location of the stolen money before turning him into the police.

When Tina visits Stanley in the station, he urges her to leave the city. Tina thanks Stanley for showing her kindness and tells him the mask was unnecessary. She attempts to flee but is kidnapped by Tyrell and forcibly taken to a charity ball at the Coco Bongo, hosted by Niko and attended by the city's elite, including the mayor. Upon arrival, the masked Tyrell kills Niko and prepares to destroy the club with a time bomb. Milo, Stanley's dog, helps Stanley escape from the station by retrieving the keys from the guard. Stanley sets out to stop Tyrell, taking Kellaway hostage.

After locking Kellaway in his car, Stanley enters the club and enlists Charlie's help, but is quickly discovered and captured. Tina tricks Tyrell into removing the mask, which is recovered and donned by Milo, who battles his way through Tyrell's henchmen as Stanley and Tyrell fight each other. Stanley retrieves the mask, uses its powers to swallow the bomb seconds before it detonates, and then flushes Tyrell down the drain of the club's ornamental fountain; the police arrive and arrest Tyrell's henchmen. Kellaway tries arresting Stanley again, but the mayor intervenes, implicating Tyrell as the Mask and praising Stanley as a hero.

The following day, Stanley, exonerated and more secure returns to the harbor bridge with Tina. Tina throws the mask into the water before she and Stanley share a kiss. Charlie tries to retrieve the mask for himself, only for Milo to swim away with it.