Insurance worker C.C. Baxter (Jack Lemmon) lends his Upper West Side apartment to company bosses to use for extramarital affairs. When his manager Mr. Sheldrake (Fred MacMurray) begins using Baxter's apartment in exchange for promoting him, Baxter is disappointed to learn that Sheldrake's mistress is Fran Kubelik (Shirley MacLaine), the elevator girl at work whom Baxter is interested in himself. Soon Baxter must decide between the girl he loves and the advancement of his career.
- Jack Lemmon as Calvin Clifford (C.C.) "Bud" Baxter
- Shirley MacLaine as Fran Kubelik
- Fred MacMurray as Jeff D. Sheldrake
- Ray Walston as Joe Dobisch
- Jack Kruschen as Dr. Dreyfuss
- David Lewis as Al Kirkeby
- Edie Adams as Miss Olsen
- Hope Holiday as Mrs. Margie MacDougall
- Joan Shawlee as Sylvia
- Naomi Stevens as Mrs. Mildred Dreyfuss
- Johnny Seven as Karl Matuschka (Fran's cab driving brother-in-law)
- Joyce Jameson as the blonde in the bar
- Hal Smith as Santa Claus in the bar
- Willard Waterman as Mr. Vanderhoff
- David White as Mr. Eichelberge
Time and Newsweek praised it, as did The New York Times film critic Bosley Crowther, who called the film "gleeful, tender, and even sentimental" and Wilder's direction "ingenious". Esquire critic Dwight Macdonald gave the film a poor review, calling it "a paradigm of corny avantgardism". Others took issue with the film's controversial depictions of infidelity and adultery, with critic Hollis Alpert of the Saturday Review dismissing it as "a dirty fairy tale".
MacMurray relates that after the film's release he was accosted by women in the street who berated him for making a "dirty filthy movie", and one of them hit him with her purse.