The courtesan Violetta Valery is hosting an opulent party for her friends. Gastone introduces Alfredo to Violetta, explaining that Alfredo is a great admirer of hers. Violetta asks the Baron, her current companion, to offer a toast. The Baron refuses so Alfredo leads the party-goers in song. The guests move into the next room, leaving an obviously ailing Violetta alone with Alfredo. Alfredo declares his love for her, but she tells him she will never allow herself to fall in love again. After the party, Violetta is surprised to find herself strongly attracted to Alfredo but she resolves to continue living a life of freedom and pleasure.

Alfredo and Violetta have been living together happily for three months. Alfredo discovers that Violetta has been selling her possessions in order to finance their household and he leaves for Paris to raise money. Germont, Alfredo’s father, arrives unexpectedly and asks Violetta to end her relationship with Alfredo, since it jeopardizes his daughter’s upcoming marriage. Violetta eventually agrees and decides to return to her life as a courtesan. Alfredo returns and she reassures him of her love, even as she is departing for Paris. She sends a note to Alfredo, informing him that she is returning to the Baron. Germont tries to reassure his distraught son, asking him to return to their home in Provençe, but Alfredo vows revenge and leaves for Paris.

Violetta’s friend Flora is giving a lively party. Alfredo soon arrives, followed by Violetta with Baron Douphol. The Baron challenges Alfredo to a card game and loses a great deal of money. Alfredo tries to get Violetta to leave the party with him, but she refuses. Angered, Alfredo summons the party guests and throws the money he has won at Violetta’s feet. The Baron challenges Alfredo to a duel.

Violetta is mortally ill. Both Germont and Alfredo are now traveling to Paris in order to see her, but Violetta wonders whether she will live until their arrival. Alfredo rushes in and they declare their mutual love. Alfredo begins to describe a new life he has planned for them away from Paris, but it is obvious that Violetta’s death is imminent. Violetta gives her portrait to Alfredo, with the hope that he will find a “gentle maiden” to marry. After a final moment of strength, she dies.