The protagonist, Leigh Marcus Botts, introduces the characters in Dear Mr. Henshaw through the letters that he writes to children's book author Boyd Henshaw and, later, through the diary that he keeps. Leigh describes himself as "just a plain boy. . .the mediumest boy in the class." While the school does not consider him to be "Gifted and Talented," he is "not stupid either."

Bright, sensitive, thoughtful, and a bit of a loner, Leigh classifies himself as "Just a boy nobody pays much attention to." The author, Henshaw, is revealed only through Leigh's responses to his letters. Henshaw, exasperated with questions from school children, gives silly answers to some of Leigh's questions and includes his own set of questions. Upon receiving Leigh's answers to his own questions, Henshaw shows a more adult concern for a troubled child, and he tries to help, even though he...