Oskar Schell—nine-year-old main protagonist.
Oskar's mother—no name given, except "mother" or "Mom."
Thomas Schell—Oskar's father. He dies in the Twin Towers.
Thomas Schell—Oskar's grandfather (no junior or senior used for either Oskar’s father or his grandfather Oskar's father).
Oskar's Grandmother—no name given, except "Grandmother." The doorman refers to her as Ms. Schmidt only once in the story, her maiden name.
Ron—Oskar's mother's male friend who has lost his wife and child.
Anna—Oskar's grandmother's sister who died in Germany. She was in love with Oskar’s grandfather and was pregnant with his child.
Masako Tomoyasu—young woman who dies in Hiroshima bombing, in a video that Oskar presents to his class.
Mrs. Tomoyasu—Masako's mother.
Dr. Fein—Oskar's psychiatrist.
Stan—doorman at Oskar's apartment building.
Farley—doorman at Oskar's grandmother's building.
Simon Goldberg—Jewish intellectual who was befriended by Anna's father in Germany.
Gerald Thompson—limousine driver who take Oskar to the cemetery.
Toothpaste and The Minch—Oskar says these are his best friends, but they never appear in the novel.
William Black—the man who solves the mystery of the key.
Abby Black—William Black's ex-wife.
A.R. Black—the elderly man who lives in Oskar's building and helps Oskar search for the lock for Oskar’s key.