Rusty Parker (Hayworth) is a showgirl in a Brooklyn nightclub owned by Danny McGuire (Kelly), an ex-GI who was invalided out of World War II. Danny also lives across the hall from Rusty, and the two have romantic feelings for each other. On Friday nights, they go to Joe's Oyster Bar along with fellow club performer Genius (Silvers) and order oysters, looking for a pearl to bring them luck. This cozy routine is disrupted when Rusty wins a modeling opportunity as a cover girl for Vanity magazine.
Rusty is selected for the job largely because she reminds the publisher, John Coudair, of his lost love Maribelle Hicks. When he learns that Rusty is Maribelle's granddaughter, he takes an even more personal interest in her career. Through flashbacks, we see the story of John and Maribelle (also played by Hayworth): Maribelle was a vaudeville star at the turn of the twentieth century, and John was the son of a wealthy family. He showered her with gifts and attention, but she insisted that she didn't belong in his world—and no matter how hard he tried, he couldn't seem to make her forget a certain piano player.
John Coudair and his friend, theatrical producer Noel Wheaton, pressure Rusty to leave the nightclub for Broadway. She hesitates out of loyalty to Danny, but their relationship becomes increasingly strained. Coudair plays on Danny's insecurities, urging him to let Rusty move on to a better life, while Noel shows her his luxurious theatre to give her a taste of what he could offer her. This causes her to miss the Friday night oysters, and Danny, after tortuous self-reflection expressed by tap-dancing with a ghostly double of himself, decides to sever his relationship with her. The next day, Rusty is late for rehearsal, and Danny gives her song to another girl to perform. They argue, and Rusty storms out of the club, bound for Broadway.
Rusty becomes a star, and Noel asks her to marry him. She promises him an answer the next day and then goes to Danny's nightclub, but finds it closed. The watchman tells her that Danny and Genius are on a tour entertaining the troops. Depressed, she goes to Joe's Oyster Bar and gets drunk. When Coudair and Noel find her there, she agrees to marry Noel.
On the day of Rusty and Noel's wedding, Danny and Genius return to Joe's and order oysters. Danny finally finds a pearl, but seems uninterested in it and leaves it on his plate. Genius picks it up and takes it to John Coudair, urging him to give it to Rusty. At the wedding, as Coudair escorts Rusty down the aisle, he hands her the pearl and completes his story of his romance with Maribelle, revealing that she deserted him at the altar for her piano player. Rusty realizes that she belongs with Danny, and as the minister begins the wedding vows, she announces that she is leaving. Still dressed in her wedding gown, Rusty hurries to Joe's and is there reunited with Danny and Genius in a joyful dance.
Cover Girl provides examples of the following tropes:
- Affectionate Nickname: Danny calls Rusty "Chicken."
- As Herself:
- Betty and Veronica: For Rusty, Danny is Betty and Noel is Veronica. For Maribelle, the piano player was Betty and John was Veronica.
- Big Applesauce: The whole story takes place in New York, and the difference between Brooklyn and Fifth Avenue is important in both time periods.
- Bitch in Sheep's Clothing: Maurine seems friendly but will do just about anything to get ahead.
- Busby Berkeley Number: The "Cover Girl" number in Noel's show.
- Cruel to Be Kind: Danny tries to do this for Rusty, but she realizes she didn't need the "kindness" after all.
- Deadpan Snarker: Cornelia "Stonewall" Jackson, John Coudair's assistant (played by Eve Arden).Coudair: I want a girl with a story in her eyes.
Jackson: Drawing room or smoking room?
- Distracted by the Luxury: Rusty is very impressed by Noel's huge... theater.
- Drowning My Sorrows: Rusty at Joe's after she finds the nightclub closed. It's also mentioned that she continues to drink in the time leading up to the wedding—a hint that something is seriously wrong, as she used to be The Teetotaler according to Joe.
- Fiery Redhead: Averted; neither Rusty nor Maribelle is particularly fiery, although their hair is frequently mentioned.
- Flashback: Large portions of the film are this. Some of the scenes also qualify as Flash Back Echoes.
- Genki Girl: Based on some catty advice from Maurine, Rusty acts like one in her interview, nearly blowing her chances of getting the job. Stonewall later describes her as "a redheaded nervous breakdown" and tells Coudair, "That one isn't a girl, John—she's a leaping thyroid."
- The Heart: Genius always tries to keep their little group together.
- I'll Tell You When I've Had Enough!: Rusty at Joe's.Rusty: Give me a drink.
Joe: You've had too many now, Rusty.
Rusty: So I've had too many. Give me another one.
- Identical Granddaughter: Rusty looks exactly like her grandmother, Maribelle; both characters are played by Rita Hayworth.
- I Want My Beloved to Be Happy: Danny feels this way all along, but he struggles with the question of whether Rusty would be happier staying or going.
- Loving Details: Rusty recites to the minute how long it's been since she met Danny as a way of subtly reassuring him that she still cares about him despite her newfound fame as a model.
- Makeover Montage: Rusty has one before the photo session for her magazine cover, although she doesn't look much different when it's done.
- The Man in the Mirror Talks Back: Danny's "alter ego" dance.
- The Musical Musical: It's a backstage story, and most of the characters are professional performers.
- Musical World Hypotheses: Mostly Diegetic, with a couple of exceptions. "Make Way for Tomorrow" is Alternate Universe, and the "Alter Ego" dance is All In Danny's Head. "Long Ago and Far Away" is ambiguous—it could be Diegetic (improvised to Genius's piano playing), or it could be Alternate Universe.
- Rich Suitor, Poor Suitor: Both Maribelle and Rusty face this choice.
- Self-Made Man: Danny's work ethic. As he puts it, "You gotta get there on your feet, not your face."
- Ship Tease: Genius and Stonewall flirt a bit, but it's not resolved within the movie.
- Show Within a Show:
- Rusty stars in the imaginatively titled Noel Wheaton's Revue.
- Several numbers from the show at Danny's nightclub are also included: "The Show Must Go On," "Who's Complaining?" and "Put Me to the Test."