Maxwell Kane
Max is the narrator of the story. The son of a famous serial killer, Max has a very large and wide-set frame, as well as a very similar face to his father, making the other kids scared of him. However, he is in actuality a very kind-hearted and sensitive boy who hates his father and the terrible deeds he has committed. He becomes very good friends with Freak, becoming very sad and depressed after his death.
Kevin "Freak" Avery
Kevin, also known as "Freak", is a handicapped blonde boy who has Morquio syndrome, causing him to have to use crutches and leg braces. Kevin is extremely intelligent, as well as sarcastic, and has a lot of curiosity about the world. However, he has a seizure on his 13th birthday and dies.
Grim
"Grim" is Max's grandfather, who Max lives with. He calls him Grim because he is always very serious and unsmiling; however, he is really a very kind person just like Max. He originally only feels sorry for Kevin, but eventually he sees that Kevin is still a very clever and intelligent child.
Gram
Gram is Max's grandmother, who he also lives with. She is a very polite and courteous woman, balancing out Grim's more serious one. She takes good care of Max, and when he becomes friends with Kevin, she is very happy that he has made a good friend.