Comrades Iranoff, Buljanoff and Kopalski are sent to Paris to raise money for the Russian government by selling the confiscated jewels of the Grand Duchess Swana. Hoping to enjoy their one trip to Paris, the comrades decide to stay at a luxurious hotel instead of a cheap one until the sale is completed. When one of the hotel's waiters, the impoverished Russian count, Alexis Rakonin, overhears the comrades talking about the jewels, he immediately goes to Swana, who is now residing in Paris. Swana's lover, Count Leon d'Algout, helps her by showing the three comrades how good life in Paris can be, while simultaneously obtaining an injunction against the sale of the jewels until the French courts can determine who is the rightful owner. Because they have botched their assignment, the comrades are joined in Paris by "Envoy Extraordinary" Nina "Ninotchka" Ivanovna Yakushova, an attractive but stern woman who thinks only of Russia and duty. She chastizes the comrades for their frivolous excesses, which have included the frequent summoning of three attractive cigarette girls to their suite, and determines to complete the sale as soon as possible. Using her spare time to investigate the architectural and engineering wonders of Paris, Ninotchka accidentally meets Leon on the way to the Eiffel Tower. Neither knows the other's identity, and he flirts with her, while she determines to study him as an interesting example of decaying Western society. At his apartment, Leon's kiss elicits a clinical request from Ninotchka for another, but when they realize each other's true identity, she leaves. Leon is still interested in Ninotchka, for himself as well as Swana, and the next day follows her to a small cafe where he attempts to soften her seriousness by making her laugh at some silly jokes. Though other patrons find the jokes amusing, Ninotchka remains impassive until he gives up and, in agitated frustration, accidentally slips off his chair and falls to the floor. His loss of dignity elicits uncontrollable laughter from Ninotchka, who becomes a changed woman. Now loosened, Ninotchka buys a silly hat, which she had formerly looked upon disdainfully in the hotel lobby, and dresses stylishly to return to Leon's apartment. A short time later, he takes her out for a glamourous evening in a Parisian nightclub, which ends when a drunken Ninotchka tries to get the powder room attendants to strike, and an equally drunk Leon has to retrieve her. When they return to the hotel, Ninotchka opens the safe with the jewels and tries them on for Leon before she falls asleep. The next morning, Swana awakens her and tells her that she now has the jewels that Rakonin stole from the safe, which Ninotchka had left unlocked the night before. Swana promises to return the jewels, but only if Ninotchka returns to Russia without seeing Leon again. Though she loves Leon, Ninotchka agrees to Swana's terms because it is her duty, and leaves Paris without saying goodbye. When he learns what has happened, he tries desperately to obtain a visa to go to Russia, but fails, and even his love letters are of little solace because they arrive with the contents completely censored by the government. Ninotchka and Leon are reunited, however, when she is sent to Istanbul to sort out another botched job by Iranov, Buljanoff and Kopalski. Leon is waiting for her in the comrades' suite and convinces her not to return to Russia.