Paris, Christmas Eve, c. 1830. In their Latin Quarter garret, the near-destitute artist Marcello and poet Rodolfo try to keep warm by feeding the stove with pages from Rodolfo's latest drama. They are soon joined by their roommates - Colline, a young philosopher, and Schaunard, a musician, who brings food, fuel, and funds he has collected from an eccentric student. While they celebrate their unexpected fortune, the landlord, Benoit, comes to collect the rent. Plying the older man with wine, they urge him to tell of his flirtations, then throw him out in mock indignation at his infidelity to his wife. As his friends depart to celebrate at the Café Momus, Rodolfo promises to join them later, remaining behind to try to write. There is another knock at the door; the visitor is a pretty neighbor, Mimì, whose candle has gone out on the drafty stairway. No sooner does she enter than the girl feels faint; after reviving her with a sip of wine, Rodolfo helps her to the door and relights her candle. Mimì realizes she lost her key when she fainted, and, as the two search for it, both candles are blown out. In the darkness, Rodolfo finds the key and slips it into his pocket. In the moonlight the poet takes the girl's shivering hand, telling her his dreams. She then recounts her life alone in a lofty garret, embroidering flowers and waiting for the spring. Rodolfo's friends are heard outside, urging him to join them; he calls back that he is not alone and will be along shortly. Expressing their joy in finding each other, Mimì and Rodolfo embrace and slowly leave, arm in arm, for the café.
Amid the shouts of street hawkers, Rodolfo buys Mimì a bonnet near the Café Momus and then introduces her to his friends; they all sit down and order supper. The toy vendor Parpignol passes by, besieged by eager children. Marcello's former sweetheart, Musetta, makes a noisy entrance on the arm of the elderly but wealthy Alcindoro. The ensuing tumult reaches its peak when, trying to regain Marcello's attention, she sings a waltz about her popularity. She complains that her shoe pinches, sending Alcindoro off to fetch a new pair. The moment he is gone, she falls into Marcello's arms and tells the waiter to charge everything to Alcindoro. Soldiers march by the café, and as the bohemians fall in behind, Alcindoro rushes back with Musetta's shoes.
At dawn on the snowy outskirts of Paris, a customs official admits farm women to the city. Merrymakers are heard within a tavern. Soon Mimì wanders in, searching for the place where Marcello and Musetta now live. When the painter emerges, she tells him of her distress over Rodolfo's incessant jealousy. She says she believes it is best that they part. Rodolfo, who has been asleep in the tavern, wakes and comes outside. Mimì hides nearby, though Marcello thinks she has gone. The poet first tells Marcello that he wants to separate from his sweetheart, citing her fickleness; pressed for the real reason, he breaks down, saying that her coughing can only grow worse in the poverty they share. Overcome with tears, Mimì stumbles forward to bid her lover farewell as Marcello runs back into the tavern hearing Musetta's laughter. While Mimì and Rodolfo recall past happiness, Musetta dashes out of the inn, quarreling with Marcello, who has caught her flirting. The painter and his mistress part, hurling insults at each other, but Mimì and Rodolfo decide to remain together until spring.
Now separated from their girlfriends, Rodolfo and Marcello lament their loneliness in their garret. Colline and Schaunard bring a meager meal; to lighten their spirits the four stage a dance, which turns into a mock duel. At the height of the hilarity Musetta bursts in to tell them that Mimì is outside, too weak to come upstairs. As Rodolfo runs to her aid, Musetta relates how Mimì begged to be taken to her lover to die. The poor girl is made as comfortable as possible, while Musetta asks Marcello to sell her earrings for medicine and Colline goes off to pawn his overcoat, which for so long has kept him warm. Left alone, Mimì and Rodolfo wistfully recall their meeting and their first happy days, but she is seized with violent coughing. When the others return, Musetta gives Mimì a muff to warm her hands and prays for her life. As she peacefully drifts into unconsciousness, Rodolfo closes the curtain to soften the light. Schaunard discovers that Mimì is dead, and when Rodolfo at last realizes it, he runs to her side, repeatedly calling her name.