The Marschallin and her young lover Octavian have spent the night together. The Marschallin’s servant Mohammed arrives with breakfast and Octavian hides. When loud voices are heard just outside the room, the Marschallin believes that her husband has returned unexpectedly and Octavian hides again. He reappears disguised as a chambermaid, ‘Mariandel’, just before the sudden arrival of Baron Ochs, the Marschallin’s cousin, who has come to discuss his engagement to young Sophie von Faninal, daughter of a wealthy merchant who has been recently elevated to the nobility. Ochs asks the Marschallin to recommend a young man to deliver the traditional silver engagement rose to Sophie. She suggests Octavian, showing Ochs his picture, and Ochs, noticing his resemblance to ‘Mariandel’, assumes she is Octavian’s illegitimate sister. Ochs propositions ‘Mariandel’, who evades him and flees as soon as possible.
The Marschallin holds her morning levee. An Italian tenor sings to her while Ochs works on his marriage contract with the Marschallin’s notary. An Italian scandal-monger, Valzacchi, tries to sell the Marschallin the latest scandal sheets. Interrupting the tenor’s song, Ochs commands the notary to demand a dowry from Sophie’s family. Valzacchi and his niece Annina offer their services to Ochs.
After her visitors leave, the Marschallin recalls her own early marriage and muses on her fleeting youth and the inconstancy of men. Octavian returns in his own clothing, and she tells him that one day he will leave her, which he resists. She sends Octavian away but then realises that she has forgotten to kiss him goodbye. She sends servants after him, but he is already gone. The Marschallin summons Mohammed to take the silver rose to Octavian to deliver to Sophie.
Faninal and his daughter Sophie await the arrival of the rose bearer. As her duenna Marianne reports on the approach of Octavian, Sophie worries over her impending marriage to a man she has never met, Octavian arrives and presents the silver rose to Sophie, and the two youngsters become infatuated.
After a conversation chaperoned by Marianne, Sophie and Octavian are joined by Ochs and Faninal. Though they have never officially met, Ochs is overly familiar with Octavian and goes on to inspect Sophie like property. Ochs’s followers chase Faninal’s staff, causing an uproar. Octavian promises to help Sophie, and the two embrace. They are discovered by Valzacchi and Annina, who report it to Ochs, who is merely amused, considering Octavian no threat. Octavian challenges Ochs to a duel. In the fight, Ochs is slightly wounded but cries bloody murder. Sophie tells her father she will never marry Ochs. But Faninal insists, threatening to send Sophie to a convent, and ejects Octavian. Ochs, left alone, is cheering himself with a drink when Annina arrives bearing a letter for Ochs from ‘Mariandel’ requesting a rendezvous.
Valzacchi and Annina have transferred their allegiance to Octavian and help him prepare a trap for Baron Ochs at the site of his imminent meeting with ‘Mariandel’. Ochs arrives and attempts to seduce the chambermaid, but is unnerved by her resemblance to Octavian. The antics of Octavian’s accomplices make Ochs think he is hallucinating. Then Annina, in disguise, enters with a gaggle of children, claiming that Ochs is her husband and the children’s’ father. The police arrive and, to avoid a scandal, Ochs claims that ‘Mariandel’ is his fiancée Sophie. Octavian secretly lets the Police Inspector in on the plot. Faninal arrives, irate to be embroiled in such a scandal, and he sends for the real Sophie. When the Marschallin enters, the Police Inspector recognises her, having once served as her husband’s orderly. Octavian emerges, in his own clothes, and the Marschallin sends the police and all the others away. Ochs finally comprehends the truth about the Marschallin and Octavian/Mariandel. He tries to maintain his engagement to Sophie, but the Marschallin insists that he leave Vienna gracefully. Ochs departs, pursued by creditors.
The Marschallin, Sophie and Octavian are now alone. As Octavian is caught between the two women, the Marschallin understands that the day she predicted has come. She leaves to talk with Faninal. Sophie and Octavian enjoy a moment alone before leaving together. Mohammed runs in to retrieve a lost article of clothing.