Sheahan played CIAU football as a tight end and offensive tackle for the Concordia Stingers from 1975 to 1979.
[1] Sheahan began his collegiate coaching career as the assistant head coach for the McGill Redmen in 1984 and held that position until 1988, winning a Vanier Cup championship in 1987.
He was hired as head coach for the Concordia Stingers in 1989 and led the program to their first Vanier Cup appearance in 1998.
[5] However, he later joined the Guelph Gryphons on March 10, 2022, as the team's offensive line coach.
This reunited him with his son, Ryan Sheahan, who serves as the team's head coach.