Bour attended George Mason University in Fairfax, Virginia. Bour's father, mother, and older brother also attended the university. Bour's father played volleyball, his mother played softball and volleyball, and his brother, Jason, played baseball. His older brother Jason has the 12th-highest batting average in the school's history and was drafted in the 23rd round by the Cincinnati Reds in 2007.
While attending George Mason University Justin Bour also created his own legacy. He had 1,273 putouts which placed him first in the category, tied for second in career home runs with 46, third in RBIs with 187, fourth in total bases with 404, fifth in fielding percentage with .986, sixth in slugging percentage with .621, and 11th in batting average .347. During his three years at George Mason University, Bour averaged 15 home runs and 62 runs batted with an OPS better than .901. He set a school record on March 6, 2007, when he hit two grand slams and had 9 RBIs in a 28-1 victory of Coppin State. In 2008, he played collegiate summer baseball with the Bourne Braves of the Cape Cod Baseball League.