Mason pitched in the minor leagues from 1980 through 1986 in the New York Yankees and Cardinals organizations.
After retiring as a player, Mason remained with the Cardinals organization as a minor league pitching coach from 1987 through 1999. In 2000, he became the bullpen coach for the Cardinals. Mason was dismissed following the 2010 season.
Mason spent the next two years as a pitching coach in the Chicago Cubs organization. On November 17, 2012, Mason was announced as the pitching coach for the Minnesota Twins Triple-A affiliate Rochester.