On Christmas Eve in Paris two bohemian artists, Rodolfo, a poet, and Marcello, a painter, are working in their cold spartan loft (“Questo mar rosso”). Marcello suggests chopping up a chair for firewood but Rodolfo says that they should burn the play he has been working on instead. The two men are joined by Colline, a philosopher, and Schaunard, a musician. The latter has brought logs for the fire and money to buy food, earned from his recent employment by an eccentric Englishman. The four men decide to celebrate by dining at the Café Momus but before they can leave, their landlord, Benoit, knocks on the door asking for rent. They invite him in for a drink, and made garrulous by the wine, Benoit boasts of his many conquests. The four friends feign indignation over the exploits of the married man and throw him out.
Marcello, Colline, and Schaunard leave for Café Momus, while Rodolfo stays behind to finish writing an article, promising to join them shortly. There is a timid knock at the door and Rodolfo opens it to the young seamstress Mimì, who asks for a light for her candle. Seeing that she is ill and wracked with coughing, Rodolfo ushers her to a chair and lights her candle. As she is leaving, Mimì realizes that she has dropped her key and they search for it together. Rodolfo finds the key and slips it in his pocket before she notices. Mimì’s candle goes out again due to the draft and, to prolong their time together, Rodolfo blows his out intentionally and then tells her about himself and his dreams (“Che gelida manina”). Mimì replies with the story of her own modest life as a seamstress (“Mi chiamano Mimì”). The shouts of Rodolfo’s friends calling to him from the street below draw them to the window. He turns to see Mimì bathed in moonlight and is overcome by her beauty (“O soave fanciulla”). Rodolfo and Mimì declare their love and together go off to join his friends.
Outside the Café Momus the streets are filled with vendors hawking their goods and Rodolfo buys Mimì a bonnet. He introduces her to his friends and they all sit down to dinner. Marcello’s former girlfriend, Musetta, appears with the wealthy and older councilor Alcindoro. Despite Musetta’s and Marcello’s attempt to appear indifferent to each other’s presence, it is plain that they are not. She places herself at a neighboring table and tries to attract his attention by singing of the amorous attention her beauty inspires (“Quando me’n vo’”). After initially feigning irritation, Marcello surrenders to her charms. In order to rid them of Alcindoro, Musetta complains that her shoe is hurting her and sends him off to the cobbler. She falls into Marcello’s arms and joins the group of friends. When the waiter brings the bill, they realize they do not have enough to pay for their food. Musetta comes to the rescue, telling the waiter that the gentleman who was with her before will pay for this bill along with his own. As a military band approaches, the bohemians disappear into the crowd. Alcindoro returns with Musetta’s shoes to find her gone and a very large bill on his table.
Several weeks later, Mimì walks down the street looking for Marcello. She is obviously in poor health and her cough is worse. Mimì sees Marcello leaving a tavern, where he is now employed as a mural painter. She pours out her troubles to him, saying that Rodolfo is so jealous of her that she fears they must part (“O buon Marcello, aiuto!”). As Marcello attempts to comfort her, Rodolfo comes out of the tavern and Mimì quickly hides in order to avoid a confrontation. After some prodding, Rodolfo admits to Marcello that his jealous fits hide his real feelings of despair over Mimì’s increasingly serious illness. A coughing fit reveals Mimì’s presence just as Marcello, hearing Musetta’s raucous laughter, rushes back into the tavern to investigate. Rodolfo and Mimì agree to go their separate ways but sing poignantly of their love (“Donde lieta uscì”). Marcello and Musetta come out of the tavern in the midst of a heated argument. The two exchange insults and part angrily, while Rodolfo and Mimì agree to stay together until spring (“Addio, dolce svegliare”).
Months later back in their loft, Rodolfo and Marcello commiserate over their loneliness ("O Mimì, tu più non torni"). Colline and Schaunard enter, breaking the mood and offering a small meal. The four men attempt to forget their worries and frolic about the room, staging a sword fight. However, their laughter is cut short as Musetta arrives with the news that Mimì is outside, very ill, and has asked to be brought to Rodolfo. While Rodolfo helps Mimì to bed, Musetta gives her earrings to Marcello, telling him to go buy medicine and send for a doctor. She runs out to buy a muff for Mimì’s cold hands and Colline leaves to sell his coat to get more money (“Vecchia zimarra”). Left alone, Rodolfo and Mimì reminisce about their first meeting and the love that they shared. Soon the others return, bearing a muff to keep Mimì’s hands warm. As Mimì succumbs to her illness, it is obvious to everyone but Rodolfo that the help has come too late. He is the last to realize that Mimì has died and he falls on her lifeless body calling her name.