Leahy was born in 1934 in Bay City, Michigan, and attended North St. Joseph's High School.
[1] He played college football as an end and linebacker for the Colorado Buffaloes from 1954 to 1956.
He was a member of the 1956 Colorado Buffaloes football team that won the 1957 Orange Bowl.
[2][3] He was a "near unanimous choice" for the 1956 All-Big Seven Conference football team.
[4] Leahy was selected by the Detroit Lions in the seventh round (83rd overall pick) of the 1957 NFL draft.