Lieutenant Pinkerton sails to Nagasaki upon the Uss Abe Lincoln and weds Cio-Cio-San, a 15 year old geisha. The matchmaker has made all of the marriage contract and living arrangements. sharpless, a gentleman, begs Pinkerton not to go through with this because he knows that the contract is botched and it is only a game to Pinkerton. Cio-Cio-San, believing she is now American, renounces her faith and knows she can never return to her family. At the reception, Cio-Cio-San`s uncle appears and tells everyone to abandon her for abandoning her faith. She is distraught and Pinkerton lovingly consoles her. Pinkerton`s has to return to the U.S. and promises Cio-Cio-San he will be back soon. Three years pass. Goro tries to set Cio-Cio-San up with another suitor, Yamadori, but she refuses out of her love and faithfulness to Pinkerton. he Uss Abe Lincoln pulls into port and Cio-Cio-San prepares herself for Pinkerton. Pinkerton arrives with his American wife and his wife tells Cio-Cio-San the truth and she is stricken with grief.

Cio-Cio-San is asked to give her son over to the new wife to care for him. She asks that Pinkerton return in half an hour himself to retrieve the boy. She bids farewell to her son and blindfolds him and places an American flag in his little hands. Cio-Cio-San, believing she will never have honor, then takes oout her father`s dagger and plunges it into her. Pinkerton discovers Cio-Cio-San dying and cries out her name in bitter anguish.