Bruno is the naive but perceptive main character of the story. He is dark-haired and small for his age. He thirsts for adventure and discovery, and this trait leads him toward transformation. Though he resists everything about his new home at Out-With initially, his love for his friend Shmuel changes his attitude.
Shmuel is small and frail because of his poor diet and living conditions, but he is very friendly. He is also long-suffering. He complains only once—commenting on how the guards hate the prisoners. His patience and ability to derive happiness through his friendship with Bruno, despite his own living conditions, shows a child very mature for his age.
Ralf has thick dark hair and is authoritarian and dutiful. His wife Elisabeth (Elsa) knows he is kindhearted by nature. His rigid adherence to duty at the expense of his family's happiness blinds him to Bruno's situation and activity. He is the central power at Out-With, but by the end of the story, he becomes a morally defeated, disrespected man.
Gretel is a blond, pig-tailed girl who loves dolls and is at one point infatuated with Lieutenant Kotler. Her teachers in Berlin considered her very intelligent. She is grief-stricken at Bruno's disappearance at the end of the novel.
Elisabeth (Elsa) is a tall redhead who is close to her children, but her husband's duties cause her stress. To cope with her situation, she often drinks sherry. Her willingness to shield Pavel for tending to Bruno's wound shows compassion. Despite her struggle to keep the family happy, she ultimately returns to Berlin with only Gretel, and both are grief-stricken. She develops a friendship with and possibly has an affair with Lieutenant Kotler.
Lieutenant Kurt Kotler is a young blond man who is Ralf's subordinate. He is very serious and threatening. He takes control in the absence of Bruno's father but is shaken by questions about his father. This suggests that his father may be an enemy of the new German state and disapproves of Hitler. It is soon after Bruno's father questions Kotler at the dinner table about his family that Kotler is reassigned and no longer at Out-With. Kotler is a possible object of affection for both Gretel and her mother.