Atop a large hill in Nagasaki, Lieutenant Pinkerton of the United States Navy, inspects a house he recently rented from real-estate agent, Goro. Goro is also a marriage broker and has supplied Pinkerton with three servants and a geisha wife named Cio-Cio San, aka. Madama Butterfly. US Consul Sharpless enters the house breathless after climbing the large hill.

Pinkerton explains to his fried that his is a sailor living life in the moment and seeking one pleasure after the next. He tells Sharpless that he is currently infatuated with Butterfly, but his dream is to marry an American wife. And though he has a 999 year marriage contract with her, it renews from month to month and allows divorce at any time. Sharpless warns him that his Japanese fiancé may feel more passionate about their upcoming marriage than he does. Pinkerton dismisses the advice. Outside in the distance, Butterfly is happily singing about her marriage. Surrounded by her friends, she enters the house. She tells Pinkerton that her family was once wealthy, but fell on hard times. She became a geisha to earn money for her family. She shows Pinkerton some of her most treasured things and tells him she has renounced her faith and taken up Christianity. As Butterfly’s family and marriage officials arrive, Pinkerton whispers to Sharpless that this is all a farce and these new relatives will only be around for a month’s time.

After the wedding and amidst the toasts and celebrations, Butterfly’s uncle, a Buddhist priest, enters the house cursing her for abandoning her faith. Her uncle is interrupted by Pinkerton and leaves the house persuading her entire family to renounce her just as she renounced her faith. Her family leaves and servers all ties with her. Pinkerton takes hold of Butterfly and consoles her. He loves her that she is his for life. She is sad she has lost her family, but is happy in Pinkerton’s arms.

Three years have passed and Pinkerton has not returned. The servant, Suzuki, is praying to Buddha that Butterfly’s tears will dry up. After hearing her prayers, Butterfly tells Suzuki that the Japanese gods are worthless, and only her Christian god will bring Pinkerton home. Suzuki explains to Butterfly that the little money they have is about to run out. Butterfly tells her to have faith. Pinkerton will return, because he had arranged the American Consul to provide rent money, mosquito netting, and locks to keep out family and intruders. Pinkerton told her that he will one day (“Un bel di“) return with roses in hand when robins build their nests. At this, Suzuki weeps. Sharpless arrives moments later with a letter for Butterfly. It is from Pinkerton. Before he can read the letter, she asks questions as to his health and return. Overjoyed Pinkerton is in good health, she tells Sharpless that Pinkerton said he will return when the robins build their nests. She asks if the robins have built their nests in America yet, because they have built their nests three times in Japan. She tells Sharpless that Goro has brought many suitors to her for marriage, but she has refused each one including the most recent – a wealthy prince. As Sharpless mentions the idea that Pinkerton may not return, she brings out her son, Dolore. She tells him that once Pinkerton learns of his son, he will surely return. If he does not, she would rather die. Saddened and moved by her devotion, Sharpless is unable to reveal the contents of Pinkerton’s letter to her. In it, Pinkerton states he is not returning to Japan. After Sharpless leaves, a cannon report is heard in the distance. Butterfly rushes to the window with her binoculars and sees Pinkerton’s ship enter the harbor. Full of excitement, she instructs Suzuki and her son to fill the house with flowers.

The following morning, Suzuki, having slept all night, enters the room with Dolore to find that Butterfly has been awaiting Pinkerton’s return and hasn’t slept at all. She persuades Butterfly to get some sleep. Butterfly agrees and takes her son into the bedroom, humming along the way. Several moments go by when Sharpless and Pinkerton knock on the front door. Pinkerton tells Suzuki not to wake Butterfly. He asks her how Butterfly knew he has returned. She tells him that Butterfly studied every ship that came into the harbor and recognized his ship when it came in the previous evening. Sharpless reminds Pinkerton that he once warned him of this impending disaster. A minute later, Suzuki sees another woman waiting outside in the garden. Her name is Kate, Pinkerton’s American wife. Suzuki falls to the floor in despair. Full of shame and remorse, Pinkerton cowardly leaves the house. Sharpless tells Suzuki that though they can do nothing for Butterfly, Kate wants to adopt Dolore as her own son and take care of him in America. Suzuki and Sharpless go outside to talk with Kate. Kate asks her to encourage Butterfly to give up her son. Butterfly wakes up and calls out to Suzuki. Suzuki come into the house crying, and Butterfly asks her what is wrong. When Butterfly sees Kate and Sharpless standing outside in the garden, she softly asks Suzuki if Pinkerton is alive. Suzuki answers yes. Butterfly knows immediately what is going on. She knows that Pinkerton has returned with his American wife and she must give up her son. Kate and Sharpless enter the house and Kate asks for Butterfly’s forgiveness. Butterfly tells her the only way she will give up her son is if Pinkerton comes to the house and asks for him in person. She sends them away and tells them to come back in half-an-hour. She tells Suzuki to draw all the curtains as there is too much light in the house and orders her into the other room. Butterfly bows before the Buddha statue and takes the dagger her father used to commit suicide and reads its inscription. “Who cannot live with honor must die with honor.” Just as she is raising the dagger, her son enters the room. She tells him how much she loves him before sending him away to play. Once he leaves, she plunges the dagger into her heart. As she lay there lifelessly on the floor, Pinkerton arrives calling out her name.