He played junior hockey for the Humboldt Indians from 1953 to 1956. In 1956-57 he turned pro with the Victoria Cougars. The Boston Bruins brought him up for part of the 1958-59 season and he stayed with them for the whole of the 1959-60 season as a checking forward. He played all of 1960-61 with the Portland Buckaroos and was back with the Bruins for part of the 1961-62 season. That was the extent of his NHL career.
Leach was a regular with the Buckaroos until his retirement in 1973. The team won the Western Hockey League championship in 1965 and 1971.
In the NHL Leach scored 13 goals and 29 assists in 126 games.
Upon retirement Larry returned to his home town of Lloydminster, Alberta where he became the first coach of the newly formed Lloydminster Border Blazers, of the Central Alberta Junior B Hockey League for the 73-74 season.