Schmidt played professional linebacker in the National Football League (NFL) for the Detroit Lions for 13 years from 1953 to 1965. He won two NFL championships with the Lions (1953 and 1957), and, between 1954 and 1963, he played in ten consecutive Pro Bowl games and was selected each year as a first-team All-Pro player. He was also voted by his fellow NFL players as the NFL's most valuable defensive player in 1960 and 1963, named to the NFL 1950s All-Decade Team, and inducted into the Pro Football Hall of Fame in 1973.