Vittorio De Sica still hadn't found the ideal actor to play Bruno when filming began. It was while he was shooting the scene in which Antonio searches for his friend who can help him locate the bike that fate intervened. "I was telling Maggiorani something," he recalled, "when I turned around in annoyance at the onlookers who were crowding around me, and saw an odd-looking child with a round face, a big funny nose and wonderful lively eyes. Saint Gennaro has sent him to me, I thought. It was proof of the fact that everything was turning out right." And so little Enzo Staiola was hired on the spot to play Bruno.
Movie director Sergio Leone worked as an assistant to Vittorio De Sica during filming. He also makes a short appearance as a seminary student standing next to Bruno and Antonio during the rainstorm.
For his cast, Vittorio De Sica chose a factory fitter, who had brought his son along for an audition, as his male lead. His leading actress was a journalist who had approached him for an interview, while the young boy was played by a child spotted in the crowd watching the filming.
Lamberto Maggiorani was very shy and embarrassed throughout the shooting, as he had no actor training and would often become anxious when he couldn't do what Vittorio De Sica wanted him to do. The director, however, did not coddle him, because he knew Maggiorani's real anxiety and nervousness before the camera would work well for his on-screen character. De Sica would later praise Maggiorani, saying "The way he moved, the way he sat down, his gestures with his hands hardened from work, the hands of a working man, not of an actor...I made him promise that after the film he would forget the cinema and would go back to his job." But during the filming, De Sica still would send a black limousine to pick Maggiorani up and bring him to the day's location.