Benioff was born David Friedman in New York City in a Jewish family. He is the son of Barbara (Benioff) and Stephen Friedman, who is a former head of Goldman Sachs. He is a distant cousin of Marc Benioff. As an adult, he changed his last name to Benioff, his mother's maiden name, to avoid confusion with other writers named David Friedman. He is the youngest of three children. His family is of German Jewish and Russian Jewish descent.
He is an alumnus of The Collegiate School and a Dartmouth College alumnus. While at Dartmouth College, he was a member of Phi Delta Alpha Fraternity and the Sphinx Senior Society - the oldest all-male secret society in the United States. At age 22, he worked as a club bouncer and then became a high school English teacher at Poly Prep in Brooklyn, New York City. Additionally, he attended the University of California Irvine and Trinity College Dublin, and received a Master of Fine Arts degree in the creative writing program.