In his lavish home, the old bachelor Don Pasquale is furious and determined to disinherit his nephew Ernesto who, despite his wishes, wants to marry the young widow Norina. Don Pasquale is eager to meet with his friend doctor Malatesta who will aid him in realising his desire – he plans to marry and have an heir, so he can cut his nephew off without a penny. When doctor Malatesta is unable to talk him out of this plan, he pretends to support Don Pasquale’s intentions, moreover, for the bride he suggests his own beautiful young sister Sofronia who will actually be impersonated by his niece Norina. Don Pasquale, unaware of the fraud, is thrilled with the offer and yearns to meet his future wife-to-be. Ernesto arrives and again refuses to marry a woman of his uncle’s choice. Don Pasquale tells him that he will have to leave the house with no inheritance and then announces his own marriage plans to his astonished nephew. Ernesto realises that his last hope to be with his loved one has vanished. To make matters worse, he learns that his friend Malatesta has arranged Pasquale’s marriage.
Norina laughs over a story about chivalrous love, because she believes that true femininity can overwhelm men. Doctor Malatesta arrives and wishes to convince Norina to take part in his plan to disillusion Don Pasquale. He explains his plan: Norina is to impersonate his (non-existent) sister Sofronia. Norina is eager to play the role if it will help her and Ernesto to be together.
The disappointed Ernesto is preparing to leave Rome while Don Pasquale is almost feverish in his awaiting for his bride-to-be. Pasquale is enchanted when Malatesta introduces his timid Sofronia. Pasquale decides to get married at once. Malatesta leaves to acquire the fake notary, his nephew Carlino and when left alone with Don Pasquale, Sofronia/Norina pretends to be restless. As soon as the doctor returns with the fake notary, the marriage contract is signed and Pasquale signs over half of his fortune to his bride. The plan almost fails because Ernesto arrives to bid farewell to his uncle and when he recognises Norina as the bride, he very nearly ruins everything. But as soon as the fake document is sealed, the false bride changes her act from a demure girl to a wilful shrew. She asks her husband to appoint Ernesto her personal attendant, asks for more servants, her own carriage and all kinds of luxuries. Don Pasquale is miserable, but it is too late; her capriciousness almost gives him a stroke.
The desperate Don Pasquale is looking at stacks of bills made by his wife and he is helpless in fighting the tyranny of his young wife. When Norina appears dressed extravagantly for the theatre, Pasquale is furious and they fight. She slaps him angrily, but then feels 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. The choir of servants merrily comments the mess going on in the house. Malatesta arrives and assures Pasquale they will trap the lovers.
In the evening in the garden, Ernesto serenades Norina, and the two declare their love. Pasquale finds them, but Malatesta succeeds to solve the entire mess by persuading Pasquale to annul the marriage and grant Ernesto his permission to marry his beloved Norina. Although they have made a fool out of him, Pasquale is overjoyed to have gotten rid of Sofronia and gives the couple his blessing.