Don Pasquale, an aging bachelor, is frustrated with his nephew, Ernesto, for refusing to marry a wealthy spinster whom Pasquale had chosen for him to marry. Instead Ernesto loves Norina, a young widow. Don Pasquale decides to spite his nephew by marrying, disinheriting Ernesto and leaving him penniless. Don Pasquale’s friend Dr. Malatesta arrives, suggesting his younger sister as a bride. He boasts that she is angelic and just out of convent. Ernesto arrives, again refusing the spinster in favor of Norina. Pasquale says that Ernesto must leave his house after gloating to him of his own plans for marriage. While reading a romance novel on her terrace, Norina receives a letter from Ernesto about his troubles with Don Pasquale. She then receives a letter from Ernesto about his troubles. Malatesta arrives, plotting on the young lovers’ behalf. He suggests that Norina im­personate his sister. She shall marry Pasquale and drive him to desperation. Norina agrees.

In Pasquale’s house, Ernesto laments his loss of Norina, clueless to Malatesta’s scheme. As Ernesto leaves, Pasquale enters, preparing himself to meet his bride-to-be. Malatesta enters with “Sofronia,” who is really the disguised Norina. The couple signs the mar­riage contract, with Pasquale granting the disguised Norina half of his estate. Ernesto enters and is dis­turbed to find Norina marrying his uncle. Malatesta quickly explains the scheme, and Ernesto agrees to stand in as the best man. As the wedding contract is signed, Norina’s tone completely changes and she becomes difficult to handle.

Pasquale is now burdened with his new wife’s spend­ing habits. As she prepares to leave for the theater and he attempts to confront her, he receives a resounding slap for his efforts. As she leaves, she drops a letter from a suitor and a rendezvous that evening. Pasquale confides in Malatesta the troubles of his marriage. The Doctor advises Pasquale to surprise the lovers, and he agrees to leave all to Malatesta.
In the garden, Ernesto serenades Norina, but they are found by Pasquale and Malatesta, just as Ernesto slips away. Norina acts innocent and refuses to leave at Pasquale’s demand. Malatesta suggests that the only way to make her leave would be for her to marry Ernesto, whom Sofronia hates. Ernesto emerges from Pasquale’s house, and Malatesta reveals that Sofronia is in fact Norina. Pasquale is happy to be freed of the imposter and he blesses the marriage of the young couple.