ACT I, Scene 1: A room in Don Pasquale's house.
The elderly, wealthy (and miserly) bachelor, Don Pasquale, wants his nephew, Ernesto, to marry a wealthy woman he has chosen for him, but Ernesto, who is in love with the beautiful but poor widow, Norina, refuses. The scheming Don Pasquale decides to get married himself, and asks Dr. Malatesta to find a suitable bride. The doctor agrees, but as he’s a friend of both Ernesto and Norina, he decides his 'help' will still allow the young couple to marry. As the Don paces nervously up and down, Maletatesta announces he has found the perfect bride and proceeds to describe her (Bella siccome un angelo — Beautiful as an angel). She is Maletatesta’s sister, Sofronia, an innocent girl raised in a convent. The enraptured Pasquale demands to meet her at once and sends Malatesta to fetch her.
Left alone, he imagines his future happiness with his wife and half a dozen children (Un foco insolito — An unusual fire). These happy musings are interrupted by Ernesto. His uncle gives him one more chance to marry the wealthy woman he has chosen, but Ernesto is determined to marry Norina. Pasquale then unloads his bombshell; he is getting married himself and Ernesto must find a new place to live! After a time, Ernesto realizes he is serious and urges him to seek the advice of Dr. Malatesta. Ernesto is dumbfounded to learn that Malatesta encouraged the marriage and provided his sister as the bride-to-be.
Scene 2: Norina's house
While reading a story of how a woman's glance captured a knight, Norina boasts that she too knows the magic of such a glance (So anch'io la virtù magica — I also know the magic power). She is waiting for Dr. Malatesta to help plot her marriage to Ernesto. A letter arrives from the oblivious Ernesto. Believing his uncle, he writes that they must give up their love and that he is leaving Rome that very day. Malatesta arrives and explains his idea to Norina. She is to pretend to be his sister, a shy, simple girl (he really does have a sister Sofronia, in a convent). Don Pasquale will fall madly in love with her, and his cousin will perform a fake ceremony (Pronta son io — I am ready). He coaches her on her behavior, and they gleefully anticipate the results of their trick (Vado, corro — I am hurrying).
ACT II: Don Pasquale's house
Ernesto bemoans his fate and vows go far away. Although that will not erase Norina from his heart, he will be satisfied if she is happy (Cercherò lontana terra -- I will seek a distant land). He leaves as Don Pasquale enters, followed by Dr. Malatesta and a heavily veiled "Sofronia". She pretends to be terrified but constantly utters scornful asides. When her veil is removed, Pasquale is so overwhelmed by her beauty, gentleness and pliability, he immediately demands a wedding. The "notary" arrives and a marriage contract is drawn up in which the besotted Pasquale promises her half of everything he possesses. She will also be the absolute mistress of the house. They are about to sign when Ernesto appears. He still has not been told of the plan and is furious at the scene that greets him. Norina and Malatesta manage to signal him to go along with the charade, and all sign the contract. Immediately the shy, docile Sofronia is gone, replaced by a shrew who prevents her new 'husband' from embracing her. She declares Pasquale is too old and too fat to take her out; Ernesto will be a more appropriate escort. She orders more servants (young, good-looking ones), a pair of carriages with horses, furniture, clothing, a dinner party for fifty, etc. Pasquale protests in vain, he is no longer the master of the house, merely a peasant bumpkin and a boor. Furiously, he realizes he has been played for a fool.
ACT III: Don Pasquale's house
Servants bustle about, and a despairing Pasquale peruses the bills. Norina is going to the theatre, and when he protests, she tells him to keep his mouth shut and go to bed. In response, he threatens divorce. As she leaves, she coyly drops a letter which arranges an assignation for that evening.
Ernesto and Malatesta discuss the rest of their plan. Ernesto will be the man Sofronia meets in the garden. After he leaves, Pasquale returns and tells Malatesta he is desperate to end the marriage, even if it means allowing Ernesto to marry his Norina. Once again, Malatesta is willing to 'help'. He and the Don will hide in the garden to observe the meeting. If Sofronia proves to be unfaithful, Pasquale will be able to throw her out.
In the garden, Ernesto sings of the evening, begging his love to come to him (Com'è gentil — How lovely). When Norina appears, they sing of their love (Tornami a dir — Tell me again). Pasquale and Malatesta try to confront the couple, but Ernesto has disappeared, and Norina swears he was never there. Once more Malatesta is called on to help and to persuade his 'sister' to leave. The doctor makes utterances loud enough for Don Pasquale to hear (she had better leave; tomorrow a new wife will come to the house, Ernesto's wife Norina) and other things, sotto voce, for her alone (telling her to pretend to fly into a rage). She agrees to go provided that Don Pasquale will allow the marriage of the young people. When Ernesto arrives, Don Pasquale tells him he is now in favor of the marriage, and he should fetch his Norina. But the bride is already there; Sofronia is Norina! Malatesta's real sister is still at the convent. They all ask his pardon for the trick they have played, and Don Pasquale ruefully says he got what he deserved. They all agree that an old man who marries is looking for trouble (La morale in tutto questo — the moral of all this).
Courtesy of San Diego Opera’s Operapaedia