McMullan joined Canada Life Group in 1998, assuming the role of managing director in 2006.
He is survived by his wife and two children.
Canada Life UK's chief executive Doug Brown praised McMullan’s leadership: "Under his stewardship, the group division became the largest insurer by premiums, employers and employees.
“These accomplishments are testament to Ian’s focus and drive as group insurance [managing director]. His business legacy is that we are the biggest and best at what we do in the group insurance marketplace, which will be much poorer without him.
“He was an outstanding leader and his high standards mean both the business and his colleagues are better for having known him. A real people person, he will be deeply missed by all those he worked with, from his colleagues to advisers and suppliers," Brown said.
Tim Stoves, who has been acting as interim managing director during McMullan’s illness, will continue in the role.