Ewart began his American football career as a college football quarterback for Yale from 1935 to 1937. After college, he continued to work in college football as a backfield coach for Wesleyan University in 1940 and Dartmouth College the following year. In 1946, Ewart began working in the National Football League as a backfield coach for the Philadelphia Eagles. Ewart was promoted to general manager for the Eagles in 1948. After the Eagles won the 1948 NFL Championship Game, Ewart became the youngest general manager to win an NFL Championship.