Outside a house in turn-of-the-century Nagasaki, Benjamin Franklin Pinkerton, an American naval officer, arranges with the marriage broker Goro to lease a residence for himself and his new bride Cio-Cio-San, also known as Butterfly. He is then introduced to Butterfly’s servants, one of whom is Suzuki. While talking to Sharpless, the American consul, Pinkerton reveals that he purchased his bride for 100 yen and that he can bow out of the marriage contract whenever he wishes. Sharpless tries to warn the officer that his teenage bride might really love him, but Pinkerton ignores the consul, drinking to the day when he will marry an American woman.
Butterfly arrives with friends and relatives, greeting Pinkerton and showing him her paltry belongings, including the dagger her father used to kill himself. She confides to Pinkerton that she secretly converted to Christianity the day before so that she could worship the same God as her husband, for whom she is willing to forget her own people.
During the wedding celebration, the Bonze, Butterflyʼs uncle, arrives. He has heard that Butterfly has renounced her religion, and he calls upon all of her relatives to renounce her. Pinkerton demands that they all leave, then comforts his new bride. As night falls, Butterfly rapturously confesses her love for Pinkerton. He leads her into the house.
Three years have passed since Pinkerton sailed away for America. The devoted Butterfly tells Suzuki that one day soon they will see Pinkerton’s ship enter the harbor. Sharpless, who has learned that Pinkerton will soon arrive in Nagasaki with a new wife, tries to persuade Butterfly to marry his client Prince Yamadori, who hopes to marry her. She refuses to listen, insisting that she is already married. Furthermore, she shows the American consul the son that she has borne Pinkerton, convinced that her husband would never abandon her or his own child. The harbor cannon announces the arrival of Pinkerton’s ship, and an elated Butterfly prepares for his imminent arrival, waiting and watching for him all night with her son and Suzuki.
Morning comes and still Pinkerton has not returned. When Butterfly carries the sleeping child to bed, Suzuki sees Sharpless, Pinkerton and an American woman—his new wife, Kate—in the garden. Suddenly overwhelmed by remorse, Pinkerton leaves, unable to face the Japanese wife he had abandoned. While Kate asks Suzuki to explain to Butterfly that Pinkerton’s son would be better off in America, Butterfly awakens and emerges, seeing the strange woman in her garden. Sharpless tells her that the woman is Pinkerton’s wife. Distraught, Butterfly sends them away, telling them that Pinkerton should come for the child in half an hour. She retreats to the house and takes her father’s dagger. She is about to stab herself when Suzuki pushes the child into the room. Butterfly parts sorrowfully from her son and sends him outside to play; she then commits suicide. Pinkertonʼs voice is heard calling in the distance as Butterfly dies.