Stephen Leach was raised in Lexington, Massachusetts and played his high school hockey at Matignon HS, where he won four consecutive Massachusetts HS hockey titles from 1981 to 1984. He went on to play two seasons at the University of New Hampshire before joining the Washington Capitals, where he spent parts of the next six seasons. He also represented the USA at the 1988 Winter Olympics.
Prior to the 1991–92 NHL season Leach was traded to the Boston Bruins in exchange for Randy Burridge. Leach recorded 31 goals with the Bruins that season and followed that with a 26-goal output the following year. Leach played over 700 NHL games with the Caps, Bruins, Blues, Hurricanes, Senators, Coyotes and Penguins.