Place: Calabria, near Montalto, on the Feast of the Assumption
Time: between 1865 and 1870

Prologue

During the overture, the curtain rises. From behind a second curtain, Tonio, dressed as his commedia character Taddeo, addresses the audience (Si può?... Si può?... Signore! Signori! ... Un nido di memorie). He reminds the audience that actors have feelings too, and that the show is about real people.

Act 1

At three o'clock in the afternoon, the commedia troupe enters the village to the cheering of the villagers. Canio describes the night's performance: the troubles of Pagliaccio. He says the play will begin at "ventitré ore", an agricultural method of time-keeping that means the play will begin an hour before sunset. As Nedda steps down from the cart, Tonio offers his hand, but Canio pushes him aside and helps her down himself.

The villagers suggest drinking at the tavern. Canio and Beppe accept, but Tonio stays behind. The villagers tease Canio that Tonio is planning an affair with Nedda. Canio warns everyone that while he may act the foolish husband in the play, in real life he will not tolerate other men making advances to Nedda. Shocked, a villager asks if Canio really suspects her. He says no, and sweetly kisses her on the forehead. As the church bells ring vespers, he and Beppe leave for the tavern, leaving Nedda alone.

Nedda is frightened by Canio's vehemence (Qual fiamma avea nel guardo), but the birdsong comforts her (Stridono lassù). Tonio returns and confesses his love for her, but she laughs. Enraged, Tonio grabs Nedda, but she takes a whip, strikes him and drives him off. Silvio, who is Nedda's lover, comes from the tavern, where he has left Canio and Beppe drinking. He asks Nedda to elope with him after the performance and, though she is afraid, she agrees. Tonio, who has been eavesdropping, leaves to inform Canio so that he might catch Silvio and Nedda together. Canio and Tonio return and, as Silvio escapes, Nedda calls after him, "I will always be yours!"

Canio chases Silvio, but does not catch him and does not see his face. He demands that Nedda tell him the name of her lover, but she refuses. He threatens her with a knife, but Beppe disarms him. Beppe insists that they prepare for the performance. Tonio tells Canio that her lover will give himself away at the play. Canio is left alone to put on his costume and prepares to laugh (Vesti la giubba – "Put on the costume").

Act 2

As the crowd arrives, Nedda, costumed as Colombina, collects their money. She whispers a warning to Silvio, and the crowd cheers as the play begins.

Colombina's husband Pagliaccio has gone away until morning, and Taddeo is at the market. She anxiously awaits her lover Arlecchino, who comes to serenade her (O Colombina) from beneath her window. Taddeo returns and confesses his love, but she mocks him. She lets Arlecchino in through the window. He boxes Taddeo's ears and kicks him out of the room, and the audience laughs.

Arlecchino and Colombina dine, and he gives her a sleeping potion to use later. When Pagliaccio returns, Colombina will drug him and elope with Arlecchino. Taddeo bursts in, warning that Pagliaccio is suspicious of his wife and is about to return. As Arlecchino escapes through the window, Colombina tells him, "I will always be yours!"

As Canio (as Pagliaccio) enters, he hears Nedda (as Colombina) and exclaims "Name of God! Those same words!" He tries to continue the play, but loses control and demands to know her lover's name. Nedda, hoping to keep to the performance, calls Canio by his stage name "Pagliaccio," to remind him of the audience's presence. He answers with his arietta: No! Pagliaccio non son! He sings that if his face is pale, it is not from the stage makeup but from the shame she has brought him. The crowd, impressed by his emotional performance, which they do not realize is real, cheers him.

Nedda, trying to continue the play, admits that she has been visited by the innocent Arlecchino. Canio, furious and forgetting the play, demands the name of her lover. Nedda swears she will never tell him, and it becomes apparent that they are not acting. Beppe asks Tonio to intervene, but Tonio refrains and prevents Beppe from halting the action. Silvio begins to fight his way toward the stage. Canio, grabbing a knife from the table, stabs Nedda. As she dies, she calls: "Help! Silvio!" Silvio attacks Canio, but Canio kills Silvio also. The horrified audience then hears the celebrated final line:

La commedia è finita! – "The comedy is finished!"