In post-WII Italy, a large crowd of men gathers around an employment office in Valmelaina. Antonio, a family man, is desperate for work in the lackluster Italian economy. The employment officer miraculously offers Antonio a job hanging up posters around the city. The job pays well, and the officer explains that Antonio will need a bicycle for the job. Unfortunately, Antonio pawned his bike to feed his family and tells the officer that he will retrieve it in a few days. Because the job can easily be offered to another prospective employee, the unsympathetic officer unequivocally tells Antonio, “No bicycle, no job.” The other men begin shouting, declaring they have bicycles and can take Antonio’s job. Desperate, Antonio lies and says he is prepared to report to work as soon as possible with a bike.
Antonio then finds his wife, Maria. He informs her of the job offer but says he can’t accept it, lamenting, “Damn the day I was born!” Maria dismisses Antonio's hysteria and pessimism; she rationally decides to sell their bed sheets for extra money. She reasons, “We can sleep without sheets,” and they later get offered 7,500 Italian lire for the linen, which is more than enough for Antonio to repossess his bike from the shop. Antonio then shows up early to meet with his boss while fiercely clutching onto his bicycle. His boss tells Antonio that he will begin his job tomorrow morning, much to Antonio’s excitement.
Before returning home, Maria wants to visit a woman at Via della Paglia. After a group of women approach Antonio and ask him where the “holy one” is, Antonio asks a child to watch his bike so he can investigate what Maria is doing there. He discovers she’s seeing a fortune teller, and Maria justifies this visit by claiming the seer predicted Antonio’s employment. Since the fortune teller’s prediction was correct, Maria now feels obligated to give her some money. Finding the whole encounter frivolous and senseless, Antonio says, "how can a woman with two children and a head on her shoulders listen to all this stupid nonsense? You must have money to throw away” to Maria. Though frustrated by Antonio’s outbreak, Maria is eventually convinced to return home without offering the seer money.
On Antonio’s first day, his co-worker instructs him on how to properly paste up posters. In this case, it’s a poster of 1940s Hollywood icon Rita Hayworth. Later Antonio becomes so engrossed in his work, he fails to pay careful attention to his bike, and a young man jumps on Antonio’s bike and quickly rides off with it. In an attempt to chase after the man, Antonio latches himself onto a moving automobile, but he loses the thief in the tunnels. Devastated, Antonio reports the stolen bike to the unsympathetic and useless police, who have Antonio file a complaint. The officer tells Antonio to search for the bike himself, to which Antonio replies, “Look all over Rome? What's the point of even filling out a complaint?" Because Antonio filed a complaint and the police received the bike’s serial number, the officer claims that they will be able to proceed with the investigation if the bike shows up, but there is not much more he or Antonio can do in the meantime.
Antonio is too ashamed to tell Maria or his young son, Bruno, the truth about his bicycle. Instead, he seeks advice from his friend, Baiocco, who’s working on a rehearsal of an amateur stage play. Baiocco tells Antonio that he should look for the bike at Piazza Vittorio, Rome’s largest square, as soon as possible.
The following morning, Antonio, Bruno, Baiocco, and Baiocco's friends visit Piazza Vittorio, where they discover countless bicycles and parts. They decide to split up and meticulously scan different pumps and tires. Believing to see a part of his bike, Antonio asks one of the sellers for the bike's serial number. The seller refuses, so Antonio returns with a cop, who demands the man to reveal the serial number. The serial number doesn't match the one belonging to Antonio's bike. Defeated, he tells the officer, “A man who's been robbed has a right to look.”
Baiocco tells Antonio to search in another market, Porta Portese, but he and the others cannot join him this time. At Porta Portese, Antonio spots an elderly man and a young man conversing, and he suddenly recognizes one of them—the younger man—as the thief. Antonio and Bruno begin to chase them, and they eventually stumble upon the older man. Antonio approaches the older man about the thief, who pretends to be oblivious and walks away.
Antonio and Bruno follow the old man into a church, and Antonio again confronts him about the young man during the service. The old man ignores Antonio and then demands that he leave. Antonio does not give up, and the old man eventually succumbs to Antonio’s persistence and tells him the address and apartment number of the young man. The old man refuses to escort them there and manages to escape from Antonio.
It’s now late afternoon, and Antonio begins to lose hope, as the chance to retrieve his bike has seemingly slipped away from him. He projects his frustration onto Bruno and slaps him when he begins to question his father. A tearful Bruno asks Antonio, “Why did you hit me?” and Antonio says Bruno deserved the punishment.
Antonio and Bruno separate to look for the old man. Near a lake, Antonio spots a crowd shouting about a drowning child. Not knowing the whereabouts of Bruno, Antonio begins to panic, but Bruno is thankfully safe and sound, and Antonio realizes how important his son is to him.
Deciding to momentarily forget about the bike, the father and son go to a restaurant. Antonio justifies this irresponsible decision, saying, “why kill myself worrying when I’ll end up just as dead anyway?” The restaurant is filled with bourgeois families, which reminds Antonio and Bruno of their lower socioeconomic status. By the end of the meal, Antonio begins to think sensibly and realizes he must find his bike if he wants to provide for his family.
Desperate, Antonio visits the same dubious fortune teller he mocked earlier in the film. He hopes that she will have an answer to his problem, but she gives him generic, cliche advice upon hearing his predicament. She tells Antonio, “Either you find it right away or you never will." Antonio than offers her some of the last of his money and leaves.
Antonio and Bruno then stumble upon the young thief immediately after their visit with the seer. Antonio chases him into a brothel and drags him out into the street. The young man denies the accusations, and the neighbors in the street form a hostile crowd and tell Antonio he can’t accuse anyone of a crime without evidence or witnesses. During the commotion, Bruno fetches a police officer. The young man then falls to the ground and begins to have a seizure once Antonio fervently attempts to force a confession out of him. The irate neighbors blame Antonio's accusations for provoking the boy’s fit.
The policeman and Antonio converse about the thief. The cop asks Antonio if he’s positive that the young man is the thief, and Antonio says he’s sure. The policeman says Antonio is fighting a worthless cause—there were not any witnesses who saw the young man steal the bike, and all the malicious neighbors would testify for the young man. Antonio leaves the area in despair, and the crowd keeps shouting at him.
Antonio and Bruno sit on a curb outside of a packed football stadium. Hundreds of bicycles surround the duo, and Antonio spots an unattended one in the distance. Conflicted, he paces back and forth and gives Bruno some money to take a streetcar home. He then approaches the unguarded bicycle and jumps on it. The outcry over his attempted theft is immediate, and Bruno—who missed the streetcar—watches his father forced off the bike by a group of men. Bruno runs into the angry crowd, weeping, “Papa! Papa!” The men begin to muscle Antonio toward the police station. The owner of the bicycle notices Bruno, and compassionately decides to not press charges against Antonio. Antonio and Bruno walk amid a crowd, and Antonio holds his head in shame, trying not to cry. Bruno tearfully grasps his father’s hand, and they continue walking home.