John Brasker Garris was born on June 6, 1959, in Bridgeport, Connecticut. He attended Bassick High School, where he made a name as a strong player in his hometown. After high school, he initially enrolled at the University of Michigan and then transferred to Boston College. He played for the Eagles in the 1981–82 and 1982–83 seasons, helping the team reach the NCAA Tournament in both years.
Garris became known for his clutch performances in big games. In the 1982 NCAA Tournament, he was selected to the All-Tournament team after Boston College upset second-ranked DePaul and advanced to the Elite Eight. The following year, he scored 25 points and grabbed 12 rebounds against Ralph Sampson in a close loss to Virginia, cementing his reputation as a tough competitor. In his senior year, he averaged a team-high 19.7 points per game. He was later inducted into Boston College’s Varsity Club Athletic Hall of Fame in 1996.