Docter was born in Bloomington, Minnesota, growing up socially isolated, preferring to work alone and having to remind himself to connect with others. He often played in the creek beside his house, pretending to be Indiana Jones and acting out scenes. A junior-high classmate later described him as "this kid who was really tall, but who was kind of awkward, maybe getting picked on by the school bullies because his voice change at puberty was very rough".