DeHaan was born in Allentown, Pennsylvania. His father, Jeff, is a computer programmer, and his mother, Cynthia Boscia, is an executive at Metlife. He has an older sister, Meghann, and had what the New York Times Magazine has described as a "very normal, super-supportive childhood." He attended Emmaus High School in Emmaus, Pennsylvania, for three years and appeared in community theater. He switched to the University of North Carolina School of the Arts for his senior year of high school, where he was "around artists for the first time." He continued at UNCSA for undergraduate studies, graduating in 2008.