The film opens with a radio broadcast where Harry Stockwell (himself) sings an excerpt of "Broadway Melody," which had been introduced in the first film of the Broadway Melody series, followed by Frances Langford (herself) crooning "You Are My Lucky Star," one of this film's most famous songs. When her vocal concludes, Bert Keeler (Jack Benny), an obnoxious gossip columnist from the World Tribune, presents his column radio-style, but all he talks about is who is having a baby. Back at the newspaper office, his editor forbids any more writing about babies and tells him to dig up some dirt or else. In his office, Keelers assistant, Snoop (Sid Silvers), sees theatrical producer, Bob Gordon (Robert Taylor), dancing with the wealthy widow, Lillian Brent (June Knight), on a rooftop across the street. She offers to finance Gordons new show and appeals to him to not forget about her while he works on his show. That leads into the song "I've Got a Feeling You're Fooling" sung by Bob and Lillian (later at an audition for Bobs show, Frances Langford sings a short reprise of the song). During their rendition, flowers, furniture, a piano, and a table complete with a meal, magically pop out of the floor. A girls chorus sings and watches Basil (Nick Long, Jr.), Bobs assistant, tap. He magically makes the white clad girls disappear and replaces them with the same group of girls dressed in black. Basil performs a very acrobatic dance before he dances with Lillian. The girls chorus sings again as the number ends with Lillian and Bob at the bar. After watching all of this, Bert Keeler quickly surmises that "any time a wealthy Park Avenue widow gets chummy with a Broadway guy, one of them's got something the other wants." In the next scene, Irene Foster (Eleanor Powell) arrives at Bobs office. She explains to his secretary, Kitty Corbett (Una Merkel), that she and Bob had been high school sweethearts five years ago in their hometown of Albany. Keeler comes to Bob's office after a scoop, but instead encounters a man whose talent was snoring (Robert Wildhack), which he gladly demonstrates. For some unknown reason, this snoring man is a recurring annoyance several times during the film. When Bob breezes into his office, he doesnt recognize Irene. As Irene is unpacking in her newly rented tenement apartment, she hears tap dancing on the roof and goes to investigate. She finds Ted (Buddy Ebsen) and Sally (Vilma Ebsen), a brother and sister act, preparing to eat breakfast at noon. Ted tells her it's cheaper to eat that way. While waiting for their coffee to brew, the duo performs an exuberant song and tap dance routine to "Sing Before Breakfast." When it ends, Irene applauds and is invited to join them. After introductions, Ted says he doesnt believe in bad luck taboos like walking under a ladder and singing before breakfast. After some more singing, the long-legged Irene performs a solo. All three join in the fun again and sing and dance their exit. When Bob's secretary helps him remember Irene, he orders Kitty to find her, so she convinces Snoop to ask Keeler to print in his column that Bob is looking for Irene. The wealthy widow, Lillian, burst into Bob's office furious about Keeler's less-than-flattering column about their relationship. Bob dashes down to the columnists office to punch him (similar to the recurrence of the snoring man, Bob punching Keeler occurs several times during the film). Ted and Sally show Keeler's next column about Bob looking for her to Irene, but she stubbornly refuses to see him again, however, she eventually relents and shows up at the audition for the show. Bob takes her aside and discourages her from getting mixed up in the sordid show business world. When he is called to his office, Irene is left sitting alone in the audience. She imagines what it would be like to sing and dance in the theater ("You Are My Lucky Star," Miss Powell's vocals were dubbed by Marjorie Lane). During the number, Irene dances in a ballet in toe shoes. Back in Bob's office, Lillian, his wealthy backer, now wants to be the show's leading lady. To be a success, he thinks the show needs a star, but promises if he can't find one in two weeks he'll allow Lillian to star. Bob leaves for the West Coast to search for his star. Keeler suggests to Kitty that Bob get LaBelle Arlette, a French actress he invented, as his star. Keeler continues the charade by building his invention up in his columns and on his radio show; he even rents a room for her at the Hotel Carlton. When Bob returns empty handed from his Hollywood venture, Kitty tells him about LaBelle Arlette and asks why he doesn't hire her. Bob gives Ted and Sally parts in his production and sends Irene back to Albany by train, but she gets off the train to meet Kitty; they have something cooked up. In the next scene, Ted and Sally perform a dress rehearsal of their number in Bob's show, "On a Sunday Afternoon," a Gay Nineties-type number. Just as Gordon gives in to Lillian's demands to star, Irene shows up at his office as LaBelle Arlette; Bob doesn't recognize her again. He quickly signs her for his show. When that news makes the newspapers, Keeler wonders how it could possibly be true since there is no real Arlette. Next during a rehearsal for Bob's show, LaBelle/Irene dances to a jazzy piano rendition of "You Are My Lucky Star," but, when that doesnt work out well, she taps exquisitely without any accompaniment. A complication arises when the real Arlette wires the World Tribune threatening to sue if they continue writing about her, which causes Keeler to call a meeting with the fake Arlette in his office. By the end of the meeting they have a plan. Bob is throwing a banquet for Arlette that evening. Irene, not Arlette, shows up with Keeler. During the evening's floor show, Frances Langford, in a glittery tux outfit, sings "Broadway Rhythm." Once Miss Langford's solo ends, Ted and Sally dance, then, lots of black or white clad dancers flood the stage. Basil, Bob's assistant, and Lillian ballroom dance until Irene, in silver tails and sequined top hat, enters to tap to a duo piano accompaniment. It turns into a big, impressive number with a flashy ending. As the film ends, Keeler calls his story into the newspaper; the snoring man appears one last time, and Bob and Irene kiss.