Oskar is a patient in a psychiatric hospital who recounts his life story by playing a tin drum to access his memories. Born with a fully developed adult consciousness, he decides on his third birthday to stop growing physically as a protest against the adult world. He wields his tin drum to communicate and possesses a piercing voice capable of shattering glass. His observant, often detached nature allows him to document the eccentricities and dark realities of his family in pre-war Danzig.

Jan is Agnes's cousin and an employee at the Polish Post Office in Danzig. His Kashubian heritage and Polish identity make him a target of prejudice in the increasingly tense pre-war city. Despite his physical frailty, which exempted him from military service in World War I, he maintains a constant, affectionate presence in Agnes's life. He serves as an alternative paternal figure for Oskar, interacting with the boy on a more emotional level than Alfred does.

Agnes runs a middle-class grocery store in Danzig alongside her husband Alfred. She worked as a nurse during World War I, where she met Alfred, but her heart remains divided between him and her cousin Jan. She is a practical woman who promises Oskar his beloved tin drum, securing her position as his primary source of optimism. She regularly negotiates the awkward domestic triangle between her husband and her lover.

Maria is a teenage girl brought in to help manage the Matzerath family grocery business. She is highly capable and quickly turns the store's finances around. Despite being close in age to Oskar, she treats him like the toddler he physically resembles, bathing and caring for him without embarrassment. This maternal treatment conflicts with Oskar's intense adolescent infatuation with her.

Alfred is a Protestant grocer working in the free city of Danzig. He intends for Oskar to inherit the family business, a plan that repulses his son. Alfred is a practical, somewhat boorish man who eagerly joins the rising Nazi Party, treating it largely as a social club where he can play cards and mingle. He remains willfully oblivious to his wife's blatant affair with his close friend.

Anna is Oskar's Kashubian grandmother, known for wearing four large skirts layered atop one another at all times. She is a stoic, grounded presence in the family history who shelters outlaws and provides a physical refuge for her grandson. She maintains her agricultural roots and offers a quiet, enduring stability compared to the chaotic lives of her descendants.

Joseph is Oskar's grandfather, an outlaw who adopts false identities to escape his past. He works variously as a logger and a firefighter, struggling to outrun the law. His adventurous, rebellious spirit sets a chaotic foundation for the family's history before he vanishes entirely while fleeing authorities.

Bruno is Oskar's keeper at the psychiatric hospital. He provides Oskar with virgin paper and writing materials to draft his autobiography. He is an unmarried, childless man who occasionally assists in documenting parts of the narrative, observing his patient with a mix of curiosity and professional duty.

Bebra is a 52-year-old circus performer and little person who deeply impacts Oskar's worldview. He understands the dangers of the coming political shifts in Germany and advises Oskar to manipulate others from behind the scenes to survive. He acts as a mentor figure, showing Oskar how to utilize his physical differences to his advantage.

Markus is a Jewish toy store owner in Danzig who supplies Oskar with a steady stream of new tin drums. He is unrequitedly in love with Agnes and frequently begs her to run away with him to escape the rising prejudice in the city. He is a gentle, anxious man entirely vulnerable to the shifting political climate.

Frau Greff is the wife of a local grocer. Lacking children of her own, she enjoys dressing Oskar in baby clothes and treating him like an infant. In exchange for this indulgence, she teaches Oskar how to read using sensationalist books about historical figures, entirely underestimating his intelligence.

Greff is a local grocer and friend of Alfred. He leads a local troop of boy scouts and spends his free time obsessively tinkering with complex weighing scales for his shop. He pays little attention to his wife, allowing Oskar to spend significant unsupervised time in their household.

Herbert is a neighbor of the Matzeraths who works as a waiter and later as a museum watchman. His body is a network of scars earned from breaking up violent bar brawls. He is a quiet, unassuming working-class man who inadvertently carries the physical trauma of the conflicts surrounding him.

Klepp is a lethargic but musically inclined man who visits Oskar in the present day. He is a committed planner who contrasts heavily with Oskar's chaotic nature. He appreciates music and eventually bonds with Oskar over their shared artistic interests, forming the foundation of a jazz band.

Vittlar is a tall, willowy man who visits Oskar in the psychiatric hospital. He functions as a sounding board for Oskar's memories and occasionally acts as a witness to his actions. He is fascinated by Oskar's drumming and wishes for a similar level of notoriety in his own life.