The old bachelor Don Pasquale plans to marry in order to punish his rebellious nephew, Ernesto, who is in love with the young widow Norina. Pasquale wants an heir so he can cut the young man off without a penny. Dr. Malatesta suggests as a bride his own beautiful younger sister. The delighted Pasquale tells him to arrange a meeting at once. When Ernesto again refuses to marry a woman of his uncle’s choice, Pasquale tells him that he will have to leave the house, then announces his own marriage plans to his astonished nephew. With no inheritance, Ernesto sees his dreams evaporating. To make matters worse, he learns that his friend Malatesta has arranged Pasquale’s marriage.
Norina laughs over a silly romantic story she’s reading. She is certain of her own ability to charm a man. Malatesta, who is in fact plotting on her and Ernesto’s behalf, explains his plan to her: Norina is to impersonate the (nonexistent) bride and drive Pasquale to such desperation that he will be at their mercy. Norina is eager to play the role if it will help her win Ernesto.
Ernesto, who knows nothing of Malatesta’s scheme, laments the loss of Norina. Pasquale appears, impatient to meet his bride-to-be. The old man is enchanted when Malatesta introduces the timid “Sofronia” and decides to get married at once. During the wedding ceremony, Ernesto bursts in and accuses Norina of faithlessness, but Malatesta quickly whispers an explanation. As soon as the wedding contract is sealed and Pasquale has signed over his fortune to his bride, Norina changes her act from demure girl to willful shrew. The shocked Pasquale protests, while Norina, Ernesto, and Malatesta enjoy the success of their plan.
Pasquale’s new “wife” has continued her extravagant ways and amassed a stack of bills. When servants arrive carrying more purchases, Pasquale furiously resolves to assert his rights as husband. Norina enters, dressed elegantly for the theater, and gives him a slap when he tries to bar her way. He threatens her with divorce, while she, in an aside, expresses sympathy for the old man’s pain. As she leaves, she drops a letter implying that she has a rendezvous with an unknown suitor in the garden that night. The desperate Pasquale sends for Malatesta and leaves the servants to comment on working in a household fraught with such confusion. Malatesta then tells Ernesto to make sure that Pasquale will not recognize him when he plays his part in the garden that evening. Alone with Pasquale, Malatesta assures him they will trap “Sofronia” in a compromising situation.
In the garden, Ernesto serenades Norina. Their staged rendezvous is interrupted by Pasquale and Malatesta—too late to catch the young man, who slips into the house while “Sofronia” plays the innocent wife. Malatesta announces that Ernesto is about to introduce his own bride, Norina, into the house. “Sofronia” protests she will never share the roof with another woman and threatens to leave. Pasquale can hardly contain his joy and grants permission for Ernesto to marry Norina, with his inheritance. When Sofronia turns out to be Norina, Pasquale accepts the situation with good humor, gives the couple his blessing, and joins in observing that marriage is not for an old man.