At a Paris railway terminus, Gabriel greets his sister Jeanne, who leaves her ten-year-old daughter Zazie with him and goes off with her latest lover. [Gabriel] takes the child out to the taxi of his friend Charles, to Zazie’s dismay: she wants to go on the Métro, but the workers are on strike. They arrive at Turandot’s café, above which Gabriel lodges, and he hands the child over to his wife Albertine, who puts her to bed. [Gabriel] gets himself ready to go to work, on the way out getting into a dispute with Turandot, who is appalled by Zazie’s precocity and filthy language.
In the morning, Zazie sneaks out alone but Turandot spots her and follows her. When he tries to take her home, she accuses him of paedophilia and a crowd gathers. Turandot is obliged to slink away and, when Gabriel returns from work, over several glasses tells him what has happened. After talking to Gridoux, the cobbler next door, instead of searching, Gabriel decides to go to bed. Gridoux, a plainspoken neighbor with a wary eye on the city’s oddities, underscores the uneasy mix of routine and chaos that threads through their day.
Zazie meanwhile is happily exploring Paris, trying every Métro station but all are shut. An elegant man picks her up and takes her to the flea market, where he buys her a pair of jeans and treats her to a dish of mussels. To reward his curiosity about her, she tells him how her mother killed her father gruesomely with an axe but was acquitted. She then describes life with her mother’s lover, who got too interested in her, so she has been passed on to her uncle.
Sensing that the stranger also is getting too interested in her, she picks up her jeans and leaves. He accuses her of theft and a crowd gathers. He pretends to be a plain-clothes policeman and escorts Zazie back to her uncle’s apartment, where a surprised Gabriel submits to the fake cop’s interrogation. After a suggestion that Gabriel is prostituting the forward little girl, he is forced to reveal what his night job is: a drag act in a club. After the alleged cop then accuses Gabriel of homosexuality, he is thrown out of the flat and retreats to the bar below.
Meanwhile, the café waitress, Mado, takes lunch to Gridoux next door, who is concerned over the nosy stranger. She however wants to talk about the cabbie [Charles], who she hopes will marry her. When she goes back to her work, the stranger tries to pump the intractable Gridoux.
Gabriel and Charles now set off to show Zazie the sights of Paris. Various adventures and misunderstandings follow, particularly at the top of the Eiffel Tower. Zazie keeps annoying both men by trying to find out if her uncle is really homosexual. He however is a hit with a group of good-looking German girls, who think he is cute. As he walks along with Zazie, still pestering him over his sexuality, the two attract the attention of the overdressed widow Mouaque. Mouaque becomes intrigued with the trio and observes the mounting attention with a curious mix of amusement and desire.
The German girls descend on Gabriel and drag him onto their tour bus as their mascot, and Mouaque finds a policeman to report this kidnapping. The cop, called Trouscaillon and identical to the man who earlier accused Gabriel of pimping and illegal sex, immediately becomes the object of Mouaque’s desire. Trouscaillon enters the scene with a same-old-town-toy-town clash of appearances and intentions, intensifying the evening’s already tangled dynamics.
After various adventures and misunderstandings, the three eventually find Gabriel, who has invited the German girls to see his show that night. He then invites Mouaque and Trouscaillon to eat with him and Zazie at a restaurant. Seeking attention, Zazie does not behave well. Ringing the bar below his flat, Gabriel asks the waitress Mado to ask his wife Albertine to bring his costume to the club, as he is busy entertaining his friends. Mado tells him that the cabbie [Charles] has at last proposed, so Gabriel asks the two to join his swelling party.
At the club, Gabriel orders champagne for his friends and waits anxiously for his costume. Albertine has however fallen asleep, to be woken by the fake cop from the morning who starts another of his bizarre interrogations. When he moves from words to attempted rape, she jumps out of the window. After his drag act, for which Albertine brought him a dress just in time, he takes everybody off to a bar. What starts with a couple slapping each other turns into a massive saloon brawl, which wrecks the place and brings on an army of cops. The group are rescued by Albertine who shows them a way into the Métro tunnels, through which they can walk in safety as the system is still on strike.
In the morning, Albertine carries the sleeping child to the railway station, where her mother Jeanne regrets that she will have to find a better-performing lover. Waking up, Zazie says her experiences have made her a bit more grown-up. Outside, all the escalators of the Métro start up because the strike is over.
