Thornton made his first appearance in the 2006 Winter Olympics. He recorded three points as Canada was shut out in three of six games, losing to Russia in the quarter-final. Four years later, he was again chosen to Canada's Olympic team for the 2010 Winter Games in Vancouver. Thornton was joined by his Sharks linemates Dany Heatley and Patrick Marleau, as well as Sharks defenceman Dan Boyle, on the squad. The offensive trio of Sharks played on the same line in the Olympics, as well. Thornton registered a goal and an assist over seven games, helping Canada to a gold medal finish.