- Jean-Pierre Léaud as Antoine Doinel
- Albert Rémy as Julien Doinel, Antoine's stepfather
- Claire Maurier as Gilberte Doinel, Antoine's mother
- Guy Decomble as Sourpuss, schoolteacher
- Patrick Auffay as René Bigey, Antoine's best friend
- Georges Flamant as Monsieur Bigey, René's father
- Pierre Repp as an English teacher
- Daniel Couturier as Betrand Mauricet
- Luc Andrieux as Le professeur de gym
- Robert Beauvais as director of the school
- Yvonne Claudie as Mme Bigey
- Marius Laurey as L'inspecteur Cabanel
- Claude Mansard as the examining magistrate
- Jacques Monod as commissioner
- Henri Virlojeux as the night watchman
- Jeanne Moreau as a woman looking for her dog
- Jean-Claude Brialy as a man trying to pick up a woman
Truffaut also included a number of friends (fellow directors) in bit or background parts, including himself and Philippe De Broca in the funfair scene; Jacques Demy as a policeman; Jean-Luc Godard and Jean-Paul Belmondo as overheard voices (Belmondo's in the print works scene).
