Miss Julie takes place in the kitchen of the Count's manor house on a Midsummer's Eve. Christine, the cook, is frying something when Jean, a valet, enters, exclaiming that Miss Julie is wild tonight. He says that he danced with Miss Julie, the Count's daughter, at the local barn. Christine observes that Miss Julie has been rambunctious in the wake of her broken engagement. According to Jean, Miss Julie's fiancé abandoned her after she attempted to train him, making him jump over her riding whip in the barnyard as she beat him. Miss Julie appears in the doorway, and Jean becomes polite and charming. Julie invites him to dance. He hesitates, warning her against the dangers of local gossip, but he goes with her to the party.

A pantomime ensues in which Christine cleans the kitchen. Jean and Julie return and flirt more. Christine falls asleep next to the stove. Under Julie's orders, Jean kneels in mock gallantry and kisses her foot. In a dream, Miss Julie declares that she is "climbing down" from her social position. Jean has dreamed the opposite, yearning to improve his status. Julie asks Jean if he has ever been in love. He tells her that as a child, he got sick with love for her. He grew up on a wasteland. The Count's lovely garden was visible from his window. One day while weeding the onion beds, Jean caught sight of a "Turkish pavilion"—that is, an outhouse. Enchanted by its beauty, Jean snuck in but soon heard someone coming. Trapped, he fled through the bottom of the outhouse until coming upon a rose terrace, where Miss Julie was walking. Lovelorn, Jean watched Julie walk among the roses. The following Sunday, he went to church, determined to see Miss Julie once more, and then attempted suicide.

Moved, Julie asks Jean to take her out to the lake. Again, Jean warns her of the injury to her reputation. Suddenly the guests are heard approaching. Jean tells her that they are singing a dirty song about them and suggests that they flee to his room. They exit. The peasants dance around the kitchen. Julie and Jean return to the kitchen. The implication is that they have had sex. Gesturing toward the rumor-mongering crowd, Jean declares it is impossible to stay at the manor. He dreams of traveling to northern Italy and setting up a hotel. Julie begs Jean to declare his love. She has fallen for him. Abruptly, Jean declares that behave coolly, as if nothing has happened. Julie points out that he needs capital to open a hotel, and she has not a penny to her name. Jean says that in that case, the plans are off. Julie becomes hysterical, wondering how can she live with everyone sneering behind her back. Jean is unsympathetic, calling her a whore and revealing that his story of the rose terrace was a lie. Crushed, Julie says she deserves his abuse.

Jean proposes anew that they flee together. Julie wants to tell him about her life first. Believing in the independence of women, Julie's mother brought the estate to ruin. When Julie's father finally took command, her mother fell ill. A mysterious fire then burned down the estate. Julie's mother suggested to Julie's father that he should borrow money from a friend of hers to rebuild the farm. Jean says that Julie's mother set the fire, and the friend was her lover. Julie took her mother's side and grew up to hate men as her mother did. Jean tires of Julie's talk, and tells her she is sick. Julie begs him to tell her what to do. Terrified of the consequences with the Count, Jean commands her to flee. She exits to prepare for her departure.

Christine enters, reminding Jean that he promised to join her at church. This morning's sermon is on the beheading of John the Baptist. Jean confesses to sleeping with Julie. Disgusted, Christine decides that she cannot remain in the house. Suddenly the two hear sounds upstairs: the Count has come back. Christine exits. The sun rises, breaking the spell of Midsummer's Eve. Dressed for travel, Julie appears with a small birdcage. She begs Jean to join her. He agrees, but insists that she leave the canary behind, offering to kill it. Jean decapitates the bird on a chopping block. "Kill me too!" screams Julie. Julie approaches the chopping block, mesmerized. She exclaims that she wants to see Jean's head on a chopping block and his entire sex swimming in blood. She pledges to stay, to wait for her father and confess everything. The Count will die of shame.

Christine enters, and Julie begs her for help. Christine refuses. Desperate, Julie has an idea: the three of them can flee together and open that hotel. Christine speaks of their redemption, saying the last shall be first. Christine leaves, promising to tell the stable boy to stop any attempted departures on their part. Utterly defeated, Julie asks Jean what he would do if in her place. She picks up Jean's shaving razor and slashes the air, saying "Like this?" The bell rings twice; it is the Count. Exhausted, Miss Julie begs Jean to help her, saying she will obey him as a dog would if he helps save her father from disgrace.

Jean is immobilized by the sound of the Count's voice. Julie tells him to pretend that he is the Count, and to hypnotize her. Jean whispers the fatal instructions in her ear. Julie asks Jean to tell her that the first will receive the gift of grace. He cannot promise grace but tells her that she is definitely among the last. The bell rings twice, and Jean commands Julie to her death. She walks out the door.