Guerrier was unable to enroll at Syracuse University in January 2019 because his academic records were not presented to the National Collegiate Athletic Association (NCAA) in time. He joined the team in the following semester.[5] On February 11, 2020, Guerrier recorded a freshman season-high 16 points and 10 rebounds in a 79–74 loss to NC State.[6] As a freshman, he served as his team's sixth man, averaging 6.9 points and 5.3 rebounds per game.[7] Guerrier underwent surgery on June 2 to repair a torn muscle in his groin.[8] On December 21, he was named ACC Player of the Week after a 27-point, 11-rebound performance in an overtime win over Buffalo and an 18-point, 16-rebound effort against Northeastern.[9][10] Guerrier averaged 13.7 points and 8.4 rebounds per game as a sophomore, and had four 20-point games and 8 double-doubles. He was named to the Third Team All-ACC.
Oregon
On May 20, 2021, Guerrier announced that he would transfer to Oregon.[11]
Illinois
After two seasons with the Ducks, Guerrier announced his transfer to the Illinois Fighting Illini for his fifth and final season.[12]
His father, Steve Guerrier, played baseball in Montreal, while his mother, Saoua Melissa Lemay Nague, is a former ballet dancer. He is the oldest of four children.[1] Guerrier speaks English, French and Haitian Creole.[17]