After spending a night of love together, the Field Marshal Princess Werdenberg and her young lover, Count Octavian Rofrano, wake up. Breakfast is disturbed by an approaching male voice: Contrary to fears, it is not the Field Marshal returning home early, but Baron Ochs auf Lerchenau, an impoverished cousin of the Marschallin from the country. While Octavian disguises himself as a maid, Ochs tells the Marschallin about his wedding plans: He, otherwise not a child of sadness, wants to marry Sophie, the daughter of the extremely wealthy new noble Faninal, for the sake of consolidation. To this end, he asks the marshal to propose a professional rose cavalier who is to announce the arrival of the groom on the morning of the wedding by presenting a rose to the bride. The marshal suggests to Octavian, of which she shows Ochs a picture. He is amazed at the resemblance to the maid "Mariandl", whom he has already cast an eye on and has therefore invited her to supper.
At the Lever at the Marschallin there is a lot of hustle and bustle: there are various supplicants as well as an Italian tenor and a paper artist; Ochs argues with the notary about details of the marriage contract; the scheming couple Valzacchi and Annina offer Ochs his services.
The Marschallin has everyone thrown out and remains melancholy and upset. She argues about the young Sophie, who is about to have a marriage of convenience like hers, and her own aging. She sends the converted Octavian away with the hint that sooner or later he will leave her for a younger girl.
In the Faninal house, everyone is eagerly awaiting the arrival of the Rosenkavalier. Faninal is looking forward to the social rise associated with his marriage, Duenna Marianne Leitmetzerin about the good match and Sophie about marriage in general. Octavian enters and hands Sophie the rose, whereby both feel drawn to each other, which throws them into deep embarrassment. Sophie doesn't feel at all attracted to her future husband and his rough behavior.
When Faninal and Ochs are next door to signing the marriage contract, Octavian and Sophie admit their affection. Valzacchi and Annina catch them kissing. Ochs is not angry about this, even when Octavian informs him that Sophie does not want to marry him. But when the young adversary challenges him to a duel in a rage and injures him slightly with his sword, it triggers a tumult. Faninal throws Octavian out, fears social embarrassment and wants to force his reluctant daughter to marry.
In the meantime Ochs has struggled again and curses Octavian and the conditions in the city. His mood brightened when Annina brought him a letter from "Mariandl," who accepted his invitation.
Ochs receives »Mariandl« for supper and tries to create a romantic atmosphere. However, he feels uncomfortably reminded of Octavian during his advances. Strange apparitions throw him off track until the disguised Annina bursts in with children in tow and accuses Ochs of leaving her - his alleged wife - sitting. The noise calls the moral police on the scene. The inspector interrogates Ochs, who, cornered, pretends to be "Mariandl" as his bride, Fraulein Faninal. Then there are the real bride and her stunned father, who suffers a fit of weakness because of the scandal. While "Mariandl" is changing back into Octavian, the Field Marshal arrives as well. She appeases the commissioner, clears up the masquerade,
The marshal is left alone with Sophie and Octavian, and immediately sees through their feelings. She resigns and releases Octavian. But whether Octavian will be happy with Sophie?