His winning percentage of .864 is the second best in NCAA Division I football history, trailing only that of fellow Notre Dame Fighting Irish coach Knute Rockne, for whom Leahy played from 1928 to 1930.

Leahy served as the general manager for the Los Angeles Chargers of the American Football League (AFL) during their inaugural season in 1960.

In 1939, Leahy went to Boston College as head coach, guiding the Eagles to a 20–2 record including an undefeated 1940 season capped off with a win in the 1941 Sugar Bowl.

[1] Although he had recently signed a contract renewal at Boston College, Leahy accepted the head coaching position at his alma mater Notre Dame.

It was regarded by many as the most successful run in Notre Dame history and Leahy appeared to be well on his way of meeting his goal of ten consecutive seasons without a loss.

Leahy is one of only two coaches in college football history to have won multiple national championships at the same school during two different tenures, joining Tennessee's Robert Neyland.

Aided by freshman eligibility brought on by the Korean War, Notre Dame finished 7–2–1 in 1951 and 1952 while the 1953 squad, Leahy's last, posted a 9–0–1 docket.

Faking an injury was a widely used ploy in football as a means of buying time, but in most cases there was no impact on the outcome of a game.

A new rule was implemented the following year forbidding players from faking injuries, and many saw this as punishment directed at Notre Dame, who were branded as the "Fainting Irish.

"[2] There was some concern about Leahy's health when he collapsed from a pancreatic attack in the locker room during halftime of the 1953 Georgia Tech game.

Supposedly he had been ordered to give up coaching by his doctors for the sake of his health, but he later revealed that he left because he felt he was no longer wanted.

Leahy was succeeded by Terry Brennan, ushering in a downward slide for Notre Dame's football fortunes for the next decade.

While at Notre Dame, Leahy had six undefeated seasons, four national championship teams, and an unbeaten string of 39 games (37–0–2) in the late 1940s.

Leahy served as general manager for the Los Angeles Chargers during their inaugural 1960 season in the American Football League.