In the unheated rented garret, the painter Marcello is working on one of his pictures with icy fingers, while the poet Rodolfo, eyeing the smoking chimneys of Paris enviously, attempts to write. In order to be able to work, they try to heat the room by burning the manuscript to the poet's most recent creation. Their friend and room-mate, the philosopher Colline, comes home with a stack of books that he had fruitlessly taken to the pawnshop: it's Christmas Eve, and everything is closed. Fortunately, the musician Schaunard arrives with money and a bit of food, and as the young men happily prepare to tuck into their supper, they impulsively decide instead to dine out like gentlemen.
The preparations are interrupted by the knocking of Benoit, the landlord. After a quick consultation, Marcello superciliously admits the guest, who is there to collect the rent. To everyone's great astonishment, Marcello sits him down and offers him wine, which makes Benoît talkative. As he divulges details of his love affairs, they feign moral outrage and hustle the landlord out of the room.
The company is getting ready to go to the Latin Quarter, but Rodolfo remains at home to write an article. There is more knocking on the door: this time a young woman enters. It is Mimì, the seamstress neighbour. Her candle has gone out and she has come to ask for a flame. Rodolfo takes to the girl and offers her wine. It immediately becomes clear to both of them that they are not indifferent to one another, and soon afterwards they head out into the Christmas bustle together to find Rodolfo's friends.
Mimì and Rodolfo, now a confirmed couple, join up with their friends in the Café Momus in the Latin Quarter. Shopping, street vendors, noise and hustle and bustle. Schaunard buys a trumpet, and Rodolfo buys Mimì a bonnet. Colline has his torn coat sewn up, while Marcello courts a girl. The toy seller Parpignol arrives with a large crowd of children at his heels. Then Musetta, Marcello's former sweetheart, arrives with her wealthy, ageing benefactor, Alcindoro, but she tries to attract the attention of Marcello. As the elderly suitor becomes a burden to Musetta after a while, she attempts to get rid of him, sending him to the cobbler to fix her uncomfortable shoes. Meanwhile, the bohemians' bill is brought out, but by that point they don't have much of any money left, so Musetta cleverly smuggles it over to Alcindoro's plate, also leaving him a short message. Soldiers arrive in a ceremonial march.
Marcello and Musetta are living in a tavern on the outskirts of Paris; they do not have to pay for room and board, since Musetta sings, and Marcello provides paintings. Mimì visits Marcello and requests his help: Rodolfo is always jealous of her and quarrels with her constantly. Marcello has no advice to give her: he only has his own life to bring up as an example: take love lightly, as he does with Musetta. He shows Mimì where Rodolfo is sleeping, after having run away from Mimì after a row earlier that night and seeking refuge here. Mimì makes ready to go, but upon seeing Rodolfo just waking up, she hides herself in order to hear his words.
Rodolfo tells Marcelo that he wants to break up with Mimì, and the real cause is not jealousy, but Mimì's incurable illness and his own fear and feelings of shame. Mimì's condition is deteriorating rapidly. He blames himself because he is unable to provide her with the circumstances that she needs. Mimì hear his words clearly. When her weeping is choked by a coughing fit, Rodolfo notices her and realizes that the girl has heard every word he said. Mimì remains alone with her beloved, brokenly bidding farewell, but they nevertheless decide to remain together until spring.
We are back in the garret: Rodolfo and Marcello are trying to work, but to no avail, as their thoughts all revolve around their sweethearts. Schaunard and Colline put out some food, quickly making the atmosphere more cheerful. But this does not last long: Musetta arrives and desperately announces that Mimì, weakened by illness, can hardly make it up the stairs. Rodolfo and Marcello rush forward and lay her on the bed. Everyone surrounds the girl with love. Mimì wishes to await death with Rodolfo beside her. All she wants is a muff so that her hands won't be so cold. Musette rushes off to sell her jewelry so that she can buy one for her, while Marcello quickly pawns his recently returned coat so that they can call the doctor. Rodolfo and Mimì remain alone together and re-live their first encounter. Musetta arrives with the muff, but the girl can only enjoy it for a short time: her life will soon be over. Her death is so calm that for a moment none of them notice it. When they do, Rodolfo cries out her name in anguish.