Billingsley attended Defiance High School in Defiance, Ohio, and played for the school's baseball team. Billingsley was a high school teammate of Major League pitcher Jon Niese. He was named to the Rawlings All-American first team in his junior year as a utility player and as a pitcher in his senior year. As a senior in 2003, Billinglsey posted a 1.21 earned-run average and 138 strikeouts in 69 innings. He also had a .383 batting average with 93 runs batted in and 24 home runs as a senior. Billingsley finished high school with a state-record 502 strikeouts.