The action is set in Paris during the early 1930s.
It is Christmas Eve. Marcello, a painter, is trying to create a monotype in the extreme cold of a studio he shares with Rodolfo, a writer; Rodolfo volunteers to warm them both up by burning the manuscript of his play. Their friends arrive: Colline, despondent that he has failed to sell any books, and Schaunard, triumphant with money and food and wine. He proposes that they celebrate at the Café Momus. Just as they are about to leave, the landlord arrives with a demand for rent. They manage to avoid paying and set off, leaving Rodolfo behind to finish an article.
There is a knock at the door. It is Mimì, a neighbour, who is so weak that she faints. Rodolfo revives her and helps her to look for the key she has dropped; in the darkness, their hands touch. From the street below, Rodolfo’s friends call out for him to hurry up; he promises to join them with Mimì.
Outside Café Momus, last-minute Christmas shopping is in progress. Rodolfo introduces Mimì to his friends. Marcello loses his temper when his old flame, Musetta, walks by with Alcindoro, her companion; his upper-class impatience drives her to make an outrageous scene. Finally, she despatches Alcindoro to buy her a pair of shoes and throws herself into Marcello’s arms. The waiter arrives with the bill. As a military tattoo passes by, Musetta instructs the Bohemians to add their bill to hers: Alcindoro can settle them both.
On a cold February dawn, people enter the district looking for work. Mimì asks Marcello to speak to Rodolfo for her because his jealousy has made their life together impossible. She overhears the men talking about her: Rodolfo believes she is so ill that her only chance of recovery is to leave him and his life of poverty. Marcello and Musetta quarrel while Rodolfo and Mimì confront the necessity of separation.
It is spring. Marcello and Rodolfo are alone again, trying to work, though their thoughts stray to their absent lovers. Schaunard and Colline bring some meagre food and the four friends pretend that they are enjoying a fine dinner party with dancing. They are interrupted when Musetta bursts in to say that Mimì is dying. She wants to be with Rodolfo. The friends do what they can but it is too late to save her.