The film stars Ethel Merman, Donald O'Connor, Marilyn Monroe, Dan Dailey, Mitzi Gaynor, Richard Eastham, and Johnnie Ray. It was directed by Walter Lang and written by Lamar Trotti (story) and Phoebe Ephron and Henry Ephron. This was Ethel Merman's first film in widescreen; it was filmed in CinemaScope.
PlotIn 1919, Terrance (Dan Dailey) and Molly (Ethel Merman) Donahue, a husband-and-wife vaudeville team known as The Donahues, pursue both success and a stable family life. As the years pass, their act becomes The Five Donahues with the addition of their children, Steve, Katy and Tim. Worried that the children will suffer from their nomadic lifestyle, Molly persuades Terry to send them to a Catholic boarding school, but the youngsters, missing both their parents and the thrill of performing, continually try to run away.
Comforted by Father Dineen's assurances that the children are better off with them, Terry and Molly buy a home in New Jersey for their brood, but when the Depression hits, Terry and Molly are forced to take whatever jobs they can find, including singing for radio advertisements and working at a carnival.
Eventually, movie theaters come to their rescue by providing live stage entertainment before showings, and the Donahues are back to performing. In 1937, Tim graduates from high school, and the act becomes The Five Donahues once again, with Katy (Mitzi Gaynor) concentrating on dancing, Steve (Johnnie Ray) demonstrating an admirable singing voice, and Tim (Donald O'Connor) being an all-around performer like his father.
The family is a success and have soon hit the top, performing in a show at the famed Hippodrome Theatre in New York, where their extravagant performance of "Alexander's Ragtime Band" thrills the audience with each family member taking a turn at a themed segment.
One night after a show, a worried Molly and Terry return home alone while Katy goes out on a date, Steve takes a walk and the womanizing Tim goes out with an older chorus girl. Katy and Tim both wind up at a nightclub, Gallagher's Golden Pheasant Room, where Tim teases Victoria Hoffman, (Marilyn Monroe) a hatcheck girl about the unnatural elocution her singing teacher has instructed her to practice.
Vicky forgets Tim's wisecracks though, when Eddie, her agent, informs her that he has persuaded famed producer Lew Harris to visit the club. With the help of her co-workers, Vicky gets onstage and impresses Lew and Tim with her singing. Backstage, Vicky learns that Tim is one of the well-known Donahues, but quickly dismisses him in order to talk business with Harris.
Back at the Donahue home, Molly and Terry welcome Katy and then Steve, who informs his family that he wants to become a priest. Terry is distraught over his son's decision, but their discussion is interrupted by the appearance of Tim, who got drunk after being dismissed by Vicky. Escorting Tim upstairs to sleep it off and nearly drowning him by dunking his head into a large sink to sober him up, Molly worries aloud if he hasn't bitten off more than he can chew. Tim goes to sleep and Molly goes downstairs to deal with Katy being out all night, with her six-dollar and twenty-cent cab ride home, and with Steve's decision to become a priest.
Katy tells her father not to be so shocked and disappointed, because maybe Steve could end up a cardinal. Wailing in frustration, Terry tells the family that the only cardinal he wants in his family is one who plays ball for St. Louis (the St. Louis Cardinals).
Later, having accepted Steve's choice, the family throws him a farewell party with songs, dances and impressions, the centerpiece of which is a performance of their parents' old act by Tim and Katy. Steve tells the assembly that after his new act is worked up in the seminary after four years, he hopes everybody will come, and follows this with an uptempo jazz-influenced gospel number. Molly is crying afterward and Terry is just about to, but they both understand that eventually the bird has to leave the nest and go out on his own.
After the party, the rechristened Four Donahues accept an engagement in Miami. Upon arrival, Tim is thrilled to find that Vicky, now known as Vicky Parker, is also appearing there; however she is performing a considerably more sensual version of the same "Heat Wave" number as the family. After falling in complete lust with Vicky's performance, Tim gives his approval for her to perform the number without checking with the family beforehand.
Vicky is a sensation and, although she gently shrugs off his proposals so that she can focus on her career, Tim falls in love with her as a result. Molly, still irate that Vicky "stole" her song, is further irritated upon learning that Harris is staging a Broadway revue around Vicky, and that Vicky wants Tim and Katy to join her without Molly and Terry.
Realizing what a great opportunity this is, Terry persuades Molly to let the kids go and she agrees, on one condition. They have to take the four expensive Cuban costumes as well, originally intended for the family's version of the "Heat Wave" number they let Vicky perform instead. They all share a laugh, and soon Molly and Terry are performing on their own again while Tim and Katy rehearse with Vicky in New York.
Katy begins dating lyricist Charlie Gibbs, and after Steve is ordained, he asks whether or not Steve can perform a small wedding ceremony in the near future. Shocked and annoyed, Katy demands who Charlie plans to marry with her brother officiating, and Charlie sweetly tells her that she's the candidate. Having heard none of this in advance, Katy is pleasantly surprised and they set the date.
Tim continues dating Vicky, but one night, a wardrobe mistress passes in the hallway with a new dress, telling Vicky that Harris had selected it as her opening statement. Feeling that the dress makes the most completely inappropriate opening statement, she phones back to the club and postpones her dinner date with Tim in order to discuss the matter with Harris. The costume designer, a tall, spare haute-couture man chimes in correcting her that the color is not purple, it's `heliotrope'. Vicky angrily complains that no matter whether the dress is heliotrope, hydrangea or petunia it's still the wrong shade of purple for her, not to mention being in the most completely unflattering style. Harris, equally annoyed, reminds Vicky that the dress cost $1500, and that's not heliotrope.
Vicky loses track of time and stands Tim up, and Tim, mistakenly assuming that Vicky is having an affair with Harris, gets drunk and comes back to the theatre where he confronts Vicky about her supposed affair. Stung by the accusation, and annoyed that a fellow performer such as Tim who was born to the business of performing should chastise her for trying to follow her love of the theatre and doing whatever it took to reach her goals, Vicky denies all, but spurns Tim in his drunken state as well.
Tim leaves the theatre with one of the chorus girls, goes out and gets even more drunk as a result of being spurned by Vicky, and becomes involved in a car accident. Molly and Terry learn of the accident just hours before opening night of the show for which Vicky and Katy have been rehearsing and Terry goes down to the hospital to confront Tim about his conduct. Tim rebuffs the advice as hammish and corny, whereupon Terry slaps him across the face and storms out.
In the meantime, Molly has gone down to the theatre to be with Katy in this trying time. Lew Harris is beside himself and trying to decide if he should postpone the opening, but Molly, who has been rehearsing extensively with Katy, convinces Harris that while she'll have to fake the dancing, a feat with which she's been getting away for decades, she can go on in Tim's place.
After all is decided the show is a resounding success on opening night. The next day Terry and Molly go back to the hospital to pick up Tim but discover that he has vanished, leaving behind a note apologizing for his behavior. Molly and Terry are both heartbroken, but decide to take action.
While Molly continues to perform in the show, the Donahues hire private detectives to search for Tim, and they scour the clubs and bars of New York looking for him. After almost a year, Steve joins the Army as a chaplain, while Molly still blames Vicky for Tim's disappearance.
When Molly tells Terry that the Donahues are being sought for a benefit performance at the Hippodrome before it is closed the following May, Terry shows no interest and instead disappears by train to search for Tim. During the montage, we see him reminisce about all the good times they shared since Tim was little.
Months later, on the day of the benefit, Katy, who has become close friends with Vicky, arranges for her to share a dressing room with Molly. Annoyed at the arrangement, Molly begins to pack up and head upstairs for some peace and quiet. However, at Katy's urging, Vicky convinces Molly of her genuine love for Tim and Molly buys it.
Finally forgiving Vicky, Molly is also comforted by the arrival of Steve, who tells her not to lose hope. As Molly perform`s "There's No Business Like Show Business," Steve and Katy watch from the wings, then Tim, wearing a US Navy uniform, appears.
Molly hesitates when she sees Tim, but completes the number before running offstage to embrace her son. Tim tells her that he had to work things out for himself, and the family is finally complete when Terry joins them a few minutes later, having come to see the benefit after all. Thrilled to be reunited, The Five Donahues, with Vicky holding Tim's hand, go onstage and happily reprise their version of "Alexander's Ragtime Band."
The six principals march down a flight of stairs out of view and a chorus of men and women all in multicolored flowing attire circle around the perimeter going up and down the stairs singing the title song. The six principals then come up on a platform in the middle thereof, adding their vocals to the chorus, and the film concludes with their finale.