The opera opens at the home of courtesan Violetta Valéry, who is throwing a raucous party. One of the guests, Alfredo Germont, is introduced to Violetta and reveals that he has loved her from afar for some time, which Violetta laughs off before asking him to lead the party in a drinking song. The guests leave to dance, but Violetta is too weak due to her affliction with consumption, and Alfredo stays behind with her. Alfredo promises to love and care for her, but she makes clear that she only lives a life of pleasure. After he leaves, Violetta is somewhat overcome by his tenderness, but she resolves to stick with her earlier declarations.

Alfredo and Violetta have been living together happily in the countryside 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 leaves a note for Alfredo, informing him that she is returning to her former patron, Baron Douphol. Germont tries to reassure his distraught son, asking him to return to their home in Provence, but Alfredo vows revenge and leaves for Paris.

Alfredo arrives at a lively party thrown by Flora Bervoix, a close friend of Violetta’s. Violetta and the Baron soon appear, having reunited. 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 travel 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 think of her even after he finds someone else. After a final moment of strength, she dies.