Gelsomina (Giulietta Masina), a credulous young woman, learns that her sister Rosa has died since going on the road with the strongman Zampanò (Anthony Quinn). Now the same man has returned a year later to ask her mother if Gelsomina will take Rosa's place. The mother accepts 10,000 lire, and her daughter departs the same day.
Zampanò makes his living as an itinerant street performer, entertaining crowds by breaking an iron chain bound tightly across his chest, then passing the hat for tips. In short order, Gelsomina's naïve and antic nature emerges, with Zampanò's brutish methods presenting a callous foil. He teaches her to play the snare drum and trumpet, dance a bit, and clown for the audience. Despite her willingness to please, he relies on intimidation and even cruelty at times to maintain his dominion.
Finally, she rebels and leaves, making her way into town. There she watches the act of another street entertainer, Il Matto ("The Fool"), a talented high wire artist and clown (Richard Basehart). When Zampanò finds her there, he forcibly takes her back. They join a ragtag travelling circus where Il Matto already works. Il Matto teases the strongman at every opportunity, though he cannot explain what motivates him to do so. On being drenched by a pail of water, Zampanò chases after his tormentor with his knife drawn; as a result, he is briefly jailed and both men are eventually fired.
Gelsomina's difficulties with her forced partnership are the subject of frequent soul searching. After Il Matto's release from prison, he proposes that there are alternatives to her servitude, and imparts his philosophy that everything and everyone has a purpose—even a pebble, even her. A nun suggests that Gelsomina's purpose in life is comparable to her own. But when Gelsomina offers him marriage, Zampanò brushes her off.
The separate paths of fool and strongman cross for the last time on an empty stretch of road, when Zampanò comes upon Il Matto fixing a flat tire. As Gelsomina watches in horror, the strongman strikes the clown on the head several times. Il Matto complains that his watch is broken, then collapses and dies. Zampanò hides the body and pushes the car off the road where it bursts into flames.
The killing breaks Gelsomina's spirit. After ten days, her affect remains flat, and her eyes lifeless. Finally Zampanò abandons her while she is taking a nap, leaving some clothes and money.
Some years later, he overhears a woman singing a tune Gelsomina often played. He learns that the woman's father had found Gelsomina on the beach and kindly taken her in. However, she had wasted away and died. Zampanò gets drunk and wanders to the beach, where he breaks down in tears.