[2] He signed a baseball contract with the Pittsburgh Pirates organization and attended their spring training following his NFL rookie season.

[8] Garrett began his coaching career in the United States Army, serving as athletic director at Quartermaster Center and School at Fort Lee, from 1952 until his discharge in May 1954.

[11] Gustave Weber replaced Garrett as head coach and led Susquehanna to two losses, both against non-conference opponents, the team finished the season 0–9 overall.

He spent most of the next 40 years in the National Football League as an assistant coach with the New York Giants (1970–1973), the New Orleans Saints (1976–1977), and the Cleveland Browns (1978–1984).

He was named vice president and head coach of the Houston Texans of the fledgling World Football League, from April 1974 until the team's collapse and location move during the month of October.

[13] On December 27, 1984, he was named the head coach at Columbia University, taking over a program that had won only five of its last 63 contests and had one winning season since 1963.

His time in the school was fraught with controversy, and was forced to resign as the team went 0–10, among accusations of verbal and physical abuse.

Jason previously played and coached for the Dallas Cowboys, John is the head coach at Lafayette College, Judd is a front office executive with the Cowboys, and Jim III teaches high school English at University School.

[17] Garrett owned a beach house in New Jersey where he set up a makeshift practice field in his backyard, which he would use as an opportunity to teach the sport to his family members and other players in the nearby area.

Some of these individuals included NFL players Sam Mills, Miles Austin, Harry Flaherty Sr., Dino Hall, Bill Hill, Ethan Brooks and Darian Barnes.