In her Paris apartment, Violetta Valery is hosting a lavish party. One of her friends, Gastone, introduces her to Alfredo Germont, a young man who has long admired Violetta from afar. He joins her in a drinking song in praise of love.
As the guests go to an adjoining room to dance, Violetta suddenly nearly faints. Assuring her friends that there is no reason to worry, she urges them to go on without her. Alfredo comes in and confesses that he has been in love with her for a year. Violetta mockingly tells him that he should forget her. Her guests return to bid good night to Violetta.
As she is left alone, she muses on how strangely she is affected by Alfredo's expression of love and wonders if he could be the man who could change her life. After a moment's hesitation, she claims that it would be a folly: All she wants is freedom and hedonistic pleasure.
For three months, Violetta and Alfredo have been living in her country house near Paris. Alfredo expresses his happiness about their life together, but when he learns from Annina that Violetta sold her jewels to finance their lifestyle, he decides to go to Paris to obtain money of his own.
Entering in search of Alfredo, Violetta finds instead an invitation to a party from her friend Flora. A visitor is announced: Alfredo's father, Giorgio Germont, who tells Violetta that Alfredo's younger sister is about to be married. He demands she give up Alfredo, because their immoral affair would disgrace the family and jeopardize the girl's marriage. Violetta exclaims that she truly loves Alfredo and begs Germont not to ask such a sacrifice of her, but finally she agrees.
After Germont has left, she writes a farewell note to Alfredo and prepares to leave for Paris.
Alfredo returns. In a passionate outburst, Violetta begs him to love her, then rushes out. A servant brings Violetta's letter which devastates Alfredo. His father enters and tries to console him. Finding Flora's invitation, Alfredo suspects that Violetta has left him to return to a life of frivolity in Paris. He decides to confront her.
Flora entertains her guests at a "Spanish soiree" in her Paris apartment. Alfredo gambles at cards and pretends not to care about Violetta who arrives with Baron Douphol. The Baron challenges Alfredo to a game and loses. As the guests retire to the dining room, Violetta calls Alfredo aside and begs him to leave to avoid a scandal, but he refuses to depart without her. In a desperate attempt to keep her promise to Alfredo's father, Violetta lies to Alfredo by telling him that she is once again involved with Douphol. In a blind fury, Alfredo calls the guests back to the room and humiliates Violetta, throwing his winnings at her feet to make his point that he has "paid her in full." Germont arrives in time to witness this affront and denounces his son's behavior. Baron Douphol challenges Alfredo to a duel.
Six months later, Violetta is gravely ill with tuberculosis. Doctor Grenville tells Annina that her mistress will die before nightfall. Left alone, Violetta re-reads a letter from Giorgio Germont, saying that the duel took place and that the Baron was wounded but will recover. Alfredo has gone abroad. His father has written to him of Violetta's sacrifice. The letter assures Violetta that Alfredo will return. She fears it will be too late.
Alfredo rushes in. He begs her forgiveness. The lovers plan to leave Paris forever. Violetta desperately tries to dress so that Alfredo can take her out, but she is too weak. Germont arrives to give his blessings. Exclaiming that she feels her strenght returning, Violetta collapses dead.