Terry Brennan's athletic career started at Marquette University High School and extended to the University of Notre Dame. Brennan was an eight-letter winner in football, hockey and track at Marquette High. He captained the 1944 conference championship football team and ran the offense from his halfback position. Brennan also led the hockey team in scoring as a junior and senior and held the school pole vault and high hurdle records in track and field.
Brennan earned a scholarship to Notre Dame and started all four of his years in football as a wide receiver. He was the leading receiver and scorer on the Irish team that won the 1946 and '47 teams.
Brennan also won the 1947 middleweight collegiate boxing championship. He later returned to Notre Dame as the head football coach.