Reimer's first brush with international hockey came near the end of the 2005–06 season. He was selected to play for Team Canada at the 2006 IIHF World U18 Championships, but was unable to compete due to a broken hand he suffered while playing for Red Deer. After his strong rookie season in the NHL, Reimer received another invitation from Hockey Canada, this time to compete at the 2011 IIHF World Championship. Reimer got his first win in the tournament beating Belarus 4–1.