Larry Martin (Don Ameche) is an American entertainer working in the Casino Samba in Rio de Janeiro, Brazil. He has a skit in his show, making fun of the womanizing Baron Manuel Duarte (also Ameche in a duo role). On one particular evening, the Baron and his wife, Baroness Cecilia Duarte (Alice Faye) come to see Larry's impersonation. To the surprise of the couple, the act is amazingly realistic. Backstage, the Baron meets Larry's girlfriend, Carmen (Carmen Miranda), and invites her to a party he is going to hold. Carmen declines.
Later in the evening, Larry meets Cecilia and is attracted to her singing and her beauty. He does an impersonation of the Baron for her. But the real Baron receives a telegram that his airline is in danger because a contract is not being renewed and he has already purchased 51% of the stock. Needing money to repay the bank he borrowed it from, he flies down to Buenos Aires.
Larry is hired to play the Baron to confuse his rival, Machado (J. Carrol Naish), but at the stock market, he buys the remainder of the airline stock. That evening, at the party, Larry is hired again to play the Baron. He does not want the Baroness to know, but Cecilia is informed without his knowing. He sweeps her off her feet and they stay close to each other for the remainder of the evening.
Meanwhile, Carmen is furious to discover that Larry is at the party and decides to go there as well, where she discovers that he is impersonating the Baron. To make matter worse, the real Baron returns to his house, confusing all involved. Machado corners Larry instead and talks to him in French, which Larry can't understand. After the party, the Baron discovers that Cecilia was flirting with Larry for the evening and tries to play the joke on her. She, however, inadvertently turns the tables on him.
To get back at his wife, the next morning, the Baron calls and tells Cecilia that his plane has just landed. Cecilia is scared that she has been unfaithful to Manuel but Larry later tells her the truth. At the office, Machado gives the Baron a payment of $32 million for his airline, the topic of his conversation with Larry. The Baron heads home but Cecilia tries one more time to get back at him by pretending to make violent love to Larry. It turns out to be the Baron and all is soon resolved in the end.