Cook turned to coaching in 1937 and spent 19 years in the American Hockey League (AHL), with the Providence Reds for six seasons and the remainder with the Cleveland Barons. His 636 wins as a coach is the second most in AHL history and he led his teams to the playoffs in all but one season. Cook was named an AHL All-Star coach on six occasions, and led his teams to a record seven Calder Cup championships. He was posthumously inducted into the Hockey Hall of Fame in 1995 and to the AHL Hall of Fame in 2007.