Rudin had organized an interview with Manz. Kaufman and Price were present; they all thought she had "great character". Manz was so convincing that everyone assumed she was a real member of a street gang. Because of this, the character Peewee was specifically written for her. Many of the film's actors were unknown at the time of casting. The film was the acting debut of four cast members; Ken Wahl, Tony Ganios, Erland van Lidth and Michael Wright. It was also the feature film debut of Toni Kalem, who had previously acted on television. Kaufman intentionally cast unknown actors; someone sent a photograph of Wahl on his way to his job in a pizza parlor to Rudin, thinking he could play one of the smaller roles in the film. Kaufman felt Wahl was talented, so he cast him in the lead role, instead. To cast the role of Perry LaGuardia, Kaufman telephoned every gymnasium around New York asking for a "six-foot, four inch, 18 year-old kid". He was put into contact with Ganios, whom he cast in the role. Ganios said:  After a mysterious phone call, [my uncle] politely asked me to stop training and get dressed. He 'insisted' that I accompany him downtown to what was supposed to be a commercial audition, [but it later] turned out to be an interview for "The Wanderers". I thought acting was for sissies, but I went anyway. Filming of "The Wanderers" began in September 1978, most of it taking place in The Bronx. Kaufman said that during filming, "[This] Puerto Rican motorcycle gang came pushing its way through the crowd; wanting to see what was going on", and "they pushed everyone aside". They walked away after bumping into van Lidth. The crew also encountered trouble from former members of the "real" Baldies, who complained the film portrayed the Baldies incorrectly, saying: "[The movie] is a lie! This was not a bad neighborhood. There was no crime, no robbery. Murder, yes, but no crime!" Rose Kaufman eventually told them to "fuck off", which nearly resulted in a brawl between the former gang members, Wahl and several other actors. The final battle with the Ducky Boys, which takes place during a football game, was filmed in Van Cortlandt Park. Kaufman compared this scene to a "brutal British soccer brawl"; Ganios compared it to the Battle of Mons Graupius.