The daughter of theatrical parents goes off to sing in a musical show produced by their former cook, who loves her sister.
At a girls school Judy Bellaire (Judy Garland) updates "Spring Song" by singing "Swing, Mr. Mendelssohn, Swing" and is expelled. She is welcomed home by maid Olga Chekaloff (Fanny Brice) while her mother Diana Bellaire (Billie Burke) rehearses a love scene with Jerrold Hope (Reginald Gardiner). Her father Hillary Bellaire (Reginald Owen) fires his secretary and ignores Judy when Jack Fleming (Monty Woolley) arrives. During a singing lesson for Sylvia Bellaire (Lynne Carver) cook Ricky Saboni (Allan Jones) shows Sylvia how to sing and kisses her. Judy tells Ricky and Olga what she did. At dinner Jack criticizes Hillary's play and asks Olga. A phone call alerts Diana that Judy was expelled, but Diana plays her scene. Backer Jack walks out, and they are beset by money problems.
On his way to work Ricky sings joyfully. Ricky takes breakfast to Sylvia, and Judy says that Ricky makes money singing. Sylvia takes Jerrold to a cafe so she can hear Ricky sing. Judy sings "Down on Melody Farm," and on a bus Ricky, Sylvia, and Jerrold sing it with her. Judy tells her father she will make money. Hillary fires Ricky and sends Judy to Europe; but she hires a girl to write postcards for her and gets off the ship. Cafe owner Giovanni Vittorino (Henry Armetta) helps Ricky produce a musical show. At auditions Judy in black face sings "Way Down South." Ricky wants to send her home, but she pleads and cries. Ricky makes a record for Sylvia and sings "The One I Love." Olga listens to it and imagines her husband Boris.
Hillary replaces Jerrold, and Diana refuses to go on in the play. Hillary knocks down Jerrold and walks out. Sylvia asks Jerrold to stay and writes Ricky not to believe the newspapers; but Olga drops the letter before she finds Judy with Ricky. He hires Olga, and she sings "Quainty Dainty Me." Ricky reads that Sylvia is engaged to Jerrold. Before Diana's premiere Hillary tells her that Judy is not in Europe and cancels his play. Before Ricky's show opens, a detective arrests Judy for being only 15; but Olga has Judy holler for help, and the detective is arrested. As a clown Ricky sings "The Show Must Go On." Judy and Olga sing "Why? Because." At the police station Diana dramatizes, and the detective is brought in for kidnapping at Ricky's show. Judy sings "I Wanna Swing." Olga tells police that Jerrold is Ricky, and Jerrold is arrested. Ricky brings Sylvia on stage and sings "The One I Love." Hillary and Diana hug Judy on stage, and Boris finds Olga.
A rare film performance by Fanny Brice highlights this musical comedy that satirizes a wacky theatrical couple and entertains with fine singing.