Coles will lead the union as it works out the details of a merger with the Canadian Auto Workers union to create the largest private sector union in Canada.
The combined union, which has yet to settle on a name, will initially have more than 300,000 members across the country.
Coles beat out Wendy Sol, who served as administrative vice-president for the Western Region, to keep the job.
He said Tuesday that the union has significant work to do in not only building a new union, but a new labour movement.
Coles was first elected to the union's top job in 2006.