Leo is a nine-year-old Jewish boy living a comfortable, happy life in Vienna, Austria. He looks up to his photographer father and deeply treasures his close friendships with Max and Elsa. As political currents shift and anti-Jewish laws are introduced, Leo's innate sense of right and wrong helps him recognize the growing danger in his community, forcing him to grow up quickly to support his family.

Max is a nine-year-old boy who comes from a financially struggling and unhappy household. Isolated and bullied at school before meeting Leo and Elsa, he relies heavily on their friendship and the warm attention of Leo's father. Vulnerable to peer pressure and desperate for his own father's approval, Max finds himself drawn into the German Youth organization, where he finally receives the praise and sense of belonging he craves.

Elsa is a bright, optimistic nine-year-old Jewish girl living in Vienna. She is highly observant, noticing when her mother starts wearing gray and her parents begin speaking in hushed tones. When her family suddenly moves to Czechoslovakia to escape growing danger, Elsa adapts to her new surroundings with practical resilience, refusing to let go of her dreams for a normal future.

Mr. Grunberg is Leo's father, a professional family photographer with a warm, magnetic personality. He has a talent for making conversation with strangers and bringing out the best in children. His joyous approach to life heavily influences Leo and provides Max with a glimpse of positive fatherly affection, though his optimism is tested as anti-Jewish sentiments sweep through Austria.

Max's father is an abrasive, stressed man who frequently argues with his wife about money. Blaming his poverty on Jewish people, he embraces the rising Nazi movement and bans Max from associating with Leo and Elsa. He uses shouting and intimidation to mold his son into an obedient follower of his hateful ideology.

Leo's mother is a caring and elegant woman who manages the Grunberg household. As the political climate in Vienna becomes increasingly hostile, she struggles with anxiety and a loss of hope, relying heavily on Leo's newfound maturity to keep her going as they try to secure the necessary paperwork to leave the country.

Max's mother initially attempts to defend her son's right to play with Leo and Elsa. However, as her husband gains rank and financial stability within the Nazi party, she stops objecting to his hatred, fully embracing their new elevated lifestyle and showing Max that conformity brings rewards.

Elsa's older brother is a resilient boy with a physical disability that gives him a strong limp. He spends his time fixing broken items around the house. When their father leaves for the army, Otto bravely attempts to act as the man of the house, even trying to stand up to soldiers who commandeer their home.

Elsa's mother is a Jewish woman who carries a heavy, unspoken grief as the political situation in Austria deteriorates. She communicates in hushed tones with her husband before uprooting their family to Czechoslovakia, constantly attempting to shield her children from the full reality of their danger.

Elsa's father is a practical man who recognizes the danger facing Jewish people in Austria earlier than many others. He makes the difficult choice to abandon their home and later enlists in the army to fight against Hitler's forces, doing whatever he can to secure a future for his family.

Greta is a Jewish girl living in Prague who provides Elsa with much-needed companionship after she loses contact with Max and Leo. The two girls spend their time discussing their very different dreams for the future, with Greta hoping to one day join the resistance and fight against Hitler.

A British tourist visiting Vienna. He strikes up a warm conversation with Mr. Grunberg on the Ferris wheel and later sends a thank-you note that becomes a crucial lifeline for Leo and his mother.

A glamorous British tourist whose fashionable clothes, wide smile, and boisterous laughter captivate young Elsa. She represents a carefree, joyous adulthood that Elsa wishes to emulate.

The headmaster at Max and Leo's school in Vienna. Initially perceived as kind, he quickly reveals his loyalty to the Nazi regime by joyfully enforcing the segregation of Jewish students and referring to them as "dogs" in front of the student body.

A Jewish boy living in England who befriends Leo. Daniel's open nature and lack of fear about his own Jewish identity shock Leo, helping him realize that life can return to normal.

A Jewish girl who escaped to England on the Kindertransport. She develops a crush on Leo and eventually becomes his girlfriend, bringing renewed joy and a sense of normalcy to his and his mother's lives.