The clown Tonio delivers a prologue promising the audience that what they will see is no mere play-acting, but real life.
A village in Calabria
A crowd gathers to await the arrival of the strolling players and Canio invites them to a performance at 11 o'clock that night. As he and Beppe prepare to join the villagers at the inn, one of them warns him jokingly against leaving his wife Nedda behind with Tonio. Canio's angry reply that such goings-on are only for the play and it would be best not to play such a trick on him in real life chills Nedda. She wishes to be free of him, free like the birds flying overhead.
Tonio, a hunchback, draws near, attracted by her song, but when he declares his love, she repulses him, at first mockingly and then angrily, finally striking him with a whip when he tries to embrace her. He slinks off, vowing vengeance. But he watches as she greets her lover, Silvio, one of the villagers. She agrees to leave Canio and stay with him, and they agree to meet later that night.
Tonio has brought Canio, who overhears the assignation. Nedda delays him while Silvio escapes without being recognised. Tonio suggests that Canio bide his time, as the lover is sure to come to the performance and betray himself. Broken-hearted, Canio dresses and makes up for the performance, reminding himself bitterly that he is not a man, only a clown.
Later that night
The villagers gather and the play begins. Columbina's jealous husband Pagliaccio is away, and after rejecting the advances of Taddeo (Tonio), she entertains her lover Harlequin (Beppe).
Pagliaccio returns and begins to question Columbina. Columbina's parting words to Harlequin as he runs off are the same as Nedda used to Silvio, and Canio slips from the pretended jealousy of Pagliaccio to his own real situation. As he demands the name of her lover with increasing fury, Nedda tries to keep within the frame of the play.
Forced to confront the reality of the situation, she refuses to name her lover and is stabbed by Canio. Silvio rushes from the audience, too late to save her, and is also killed by Canio, who announces to the stunned audience: "The play is over."