The Storm, who are third in the Ontario Hockey League's Midwest Division at 23-15-2, made the announcement on the team's website Tuesday.
"I want to spend more time with my family as life has been incredibly hectic since I retired as an NHL player several years ago," Walker said in a statement.
Walker will remain co-owner of the Storm, the team said.
Walker, 41, played 17 seasons in the NHL before retiring in 2010.
He took over as head coach of the Storm that year and coached Guelph to an OHL championship in 2014. The Storm lost in the Memorial Cup final to the Edmonton Oil Kings.
Walker was also an assistant to head coach Ben Groulx on the Canadian junior men's hockey team that won gold Jan. 5.