He succeeds Wayne Sales, who stepped down from the board and his position as president and CEO.
Sales will stay on as vice chairman in an advisory capacity to Gauld.
Gauld, the past president of Canadian Tire Financial Services, retired from the company last year.
"We are delighted to have been able to entice Tom away from his very brief retirement to rejoin the company as CEO," said Gil Bennett, chairman of Canadian Tire. "Tom has skills that are applicable to the management of any business and are ideally suited to the leadership of Canadian Tire. Tom brings keen strategic insights, consumer products and customer relationship experience, an understanding of the potential of Canadian Tire’s interrelated network of businesses and an exceptional track record of developing and motivating people.”