Sage Northcutt began training in martial arts at the age of 4 and competed all over the world from a young age. His father, Mark, is a black belt in karate, and his older sister, Colbey, is an amateur kickboxing champion. At the age of 9, Northcutt became the youngest person ever to be on the cover of Sport Karate Magazine. Northcutt has won a total of 77 world youth championships in karate.
He was also an undefeated kickboxer, with his record standing at 15–0. Northcutt attended Seven Lakes High School for his first 2 years of high school before transferring to Katy High School during his sophomore year. Northcutt was inducted into the Black Belt Magazine Hall of Fame in 2012 at age 15. In High School, Northcutt was a State Medalist for wrestling.