He played junior hockey with the Calgary Canadians in 1936-37 and 1937-38 and played three seasons with Gonzaga University from 1939-42. After that McCool played with Calgary Currie Army in the 1942-43 Alberta Senior Playoffs. He joined the Toronto Maple Leafs in 1944-45 and won the Calder Trophy. He won one Stanley Cup in his career. He retired after just two years because of severe peptic ulcers. In 1945, McCool became the first goaltender in NHL history to record an assist of a goal.