A happy, laughing Cabiria (Giulietta Masina) is standing on a river bank with her current boyfriend and live-in lover, Giorgio (Franco Fabrizi). Suddenly he pushes her into the river and steals her purse which is full of money. She cannot swim and nearly drowns, but is rescued by a group of young boys and revived at the last possible moment by helpful ordinary people who live a little further down the river. In spite of just saving her life, she treats them with disdain and starts looking for Giorgio.
Cabiria returns to her small home, but Giorgio has disappeared. She is bitter, and when her best friend and neighbor, Wanda (Franca Marzi) tries to help her get over him, Cabiria shoos her away and remains disgruntled. She continues to ply her trade as a prostitute. One night, she is outside a fancy nightclub and witnesses a fight between famous movie star, Alberto Lazzari (Amedeo Nazzari), as he's dumped by his girlfriend. The differences in appearance between the glamorous girlfriend in a mink coat and the disheveled and short Cabiria are stark. The jilted Lazzari takes the starstruck Cabiria to another club and then to his house, where Cabiria is astounded by the opulence of his house. As the two are finally becoming closer after a rather standoffish few hours, Lazzari's girlfriend returns and Cabiria is shuffled off to the bathroom, unable to consummate with a movie star.
Later, a church procession passes the hangout area for the town prostitutes. As her associates mock the Church, Cabiria is drawn to the procession. Just as she is about to join the procession, another john comes and she gets in his truck instead. As she heads home later that night, she sees a man giving food to the poor people living in caves near her house. She has never seen this man before, but she is impressed by his charity towards others. When she goes to church with her friends, she prays for a chance to better her life.
Cabiria goes to a magic show, and the magician (Aldo Silvani) drags her up on stage and hypnotizes her. As the audience laughs, she acts out her desires to be married and live a happy life. Furious at having been taken advantage of for the audience's amusement, she leaves in a huff. Outside the theater, a man named Oscar (François Périer) is waiting outside to talk to her. He was in the audience and he says he agrees with her that it was not right for everyone to laugh, but believes that fate brought them together. They go for a drink, and at first she is cautious and suspicious, but after several meetings she falls passionately in love with him and they are to be married after only a few weeks. Cabiria is delighted and sells her home and takes out all her money from the bank. After they are married, she offers to give Oscar 700,000 lira cash, but he declines. However, during a walk in a wooded area, on a cliff overlooking a lake Oscar becomes distant and starts acting nervous. Cabiria realizes that just like her earlier lover, Oscar intends to push her over the cliff and steal her money. She throws her purse at his feet, sobbing in convulsions on the ground as he takes the money and abandons her.
She later picks herself up and stumbles out of the wood in tears. In the film's famous last sequence, Cabiria walks the long road back to town when she is met by a group of young people riding scooters, playing music, and dancing. They happily form an impromptu parade around her until she begins to smile through her tears.