Hugo is a twelve-year-old orphan who secretly lives in the hidden passages of a 1930s Paris train station. He survives by stealing basic necessities and spends his days winding and oiling the station's twenty-seven clocks, a job left behind by his missing uncle. Mechanically gifted and highly secretive, Hugo obsesses over repairing a broken automaton, believing it will write a message that will change his life.

Georges is an elderly, bitter man who runs a small toy booth in the Paris train station. He treats Hugo with suspicion and hostility, particularly after discovering a drawing of an automaton in the boy's notebook. He is highly protective of his private life, prone to anger, and strictly forbids his goddaughter from going to the cinema.

Isabelle is Georges's spirited goddaughter who loves reading and finding adventure in her daily life. She is intensely curious about Hugo and his notebook, seeking to uncover his secrets while guarding several of her own. She wears a unique heart-shaped necklace and frequently visits the station's bookstore.

The Station Inspector is the strict authority figure at the Paris train station. He constantly patrols the area searching for lawbreakers, thieves, and unsupervised children. He represents a constant threat to Hugo, who fears being arrested or sent to an orphanage.

Hugo's father was a skilled clockmaker who passed his mechanical knowledge and passion for machinery to his son. He died in a fire at the museum where he worked part-time. Before his death, he obsessively sketched the parts of an abandoned automaton in a notebook, which is now Hugo's most prized possession.

Uncle Claude is the Timekeeper at the Paris train station and Hugo's only living relative. He is an alcoholic who forces Hugo to live in the station walls and teaches him how to maintain the clocks and steal to survive. He disappeared months before the story begins, leaving Hugo entirely alone.

Etienne is an older friend of Isabelle who enjoys sneaking children into the local movie theater. He lost an eye in a childhood fireworks accident and wears a patch, behind which he occasionally performs a coin trick. He actively encourages Hugo's interest in magic and film.

René Tabard is an instructor at the Film Academy and the author of a book about the history of early movies. He is deeply passionate about cinema and its origins, heavily influencing his student Etienne.

Jeanne is Georges's wife and Isabelle's godmother. She shares an apartment with them and is deeply protective of her husband. She attempts to shield him from anything that might cause him stress or trigger memories of his past.

Madame Emile is the owner of the café inside the train station. She is a working-class woman who is highly protective of her inventory and watchful for the thieves who frequently target her food and supplies.

Monsieur Frick is the newspaper vendor at the train station. He frequently gossips with Madame Emile about station events and assists her in keeping an eye out for trouble or thieves in the crowded concourse.