Time: Early 1930s
Place: Catfish Row and Kittiwah Island, South Carolina

Act I 
People meet at the club run by Jasbo Brown to relax after work. In the courtyard of Catfish Row, Clara sings a lullaby to her child as the other women look on. The drug-dealer Sportin’ Life, Clara’s husband Jake, and some of the other men are playing craps. Jake sings his child a lullaby of his own. The beggar Porgy comes in to join the game; he defends Crown’s woman, Bess, about whom the others are gossiping. When Jake accuses him of being soft on her, Porgy says that he isn’t soft on any woman; God made him a cripple and meant him to be lonely.
Crown arrives with Bess and joins the dice game.  He’s drunk, and when he loses he starts a fight and kills Robbins with a cotton hook. Crown runs to hide, but tells Bess he’ll be back. Sportin’ Life offers to take her to New York with him, but she refuses.  Abandoned by Crown, Bess is shunned by the community as they await the arrival of police officers, and she accepts the help of the cripple, Porgy. Later, Porgy and Bess are at Robbins’ funeral, where his widow, Serena, is leading the mourners. The police enter and arrest Peter as a “material witness.”
Serena is still mourning as she convinces the undertaker to bury Robbins for less than his usual fee. As the scene ends, Bess leads the mourners in a spiritual as they reluctantly allow her a place in the community.
 
Act II
A few weeks later, Jake and the fishermen are working on their nets as Porgy compares his life to theirs. Maria, the matriarch of Catfish Row, chases Sportin’ Life away from her when he tries to sell his “happy dust.” Lawyer Frazier arrives and sells Bess a divorce for a dollar; when he learns that she and Crown were never married, he raises his fee to a dollar and a half. Mr. Archdale, a well-meaning white man, comes in and offers to pay Peter’s bail. All prepare to leave for the picnic. Sportin’ Life asks Bess again to come to New York with him and tries to give her more dope, which she refuses. Porgy chases him away and he and Bess sing about their newfound happiness. All except Porgy leave for the church picnic on Kittiwah Island.
 
Act III
At the picnic, Sportin’ Life sings about his own brand of religion. All are getting ready to leave when Crown, hidden in the bushes, calls out to Bess. She tells him she’s Porgy’s woman now, but he forcibly blocks her escape. Back at Catfish Row, some time later, the fishermen are getting ready to leave as Bess raves, still delirious after Crown’s attack. Peter wants to send her to the hospital, but Serena would rather pray over her. The street fills with people. Bess eventually emerges, and explains to Porgy that she wants to stay with him but that when Crown comes she’ll be forced to go with him. Porgy tells her that she doesn’t have to go with Crown.
 A hurricane begins to rise, and Clara, frightened for her husband Jake who is out fishing, calls out his name. Everyone gathers in Clara’s room and prays for shelter from the hurricane. There is a knock at the door. Crown enters and tries to take Bess away. He laughs at the frightened townspeople and sings a bawdy song to counteract their prayers. Clara sees Jake’s boat and runs out to find him. Bess calls for a man to go after her. Crown goes, after taunting Porgy and asking him why he won’t go. After the storm, the women are crying for their men; Sportin’ Life teases them and Bess. Crown enters; he and Porgy fight, and Porgy kills him. The police and the coroner come to Catfish Row the next morning; they want to take Porgy down to identify Crown’s body.
Taking advantage of Porgy's absence, Sportin' Life tells Bess that Porgy will be locked up for sure. He forces some dope on her, and leaves more outside her door as he leaves. A week later, Porgy returns; while he tries to distribute the gifts he bought with the money he made playing crap in jail, he discovers Bess is gone. He learns that she has gone off with Sportin’ Life to New York and decides to leave Catfish Row forever and follow her.