The soldier shot an IS militant dead from 3,540 metres, which is just over two miles away, in Iraq last month.
The previous record was held by British sniper Craig Harrison, who killed a Taliban fighter in 2009 in Afghanistan from 2,475 metres away (1.5 miles).
The Canadian Armed Forces now holds three of the top five positions for longest confirmed kill shots.
The unnamed soldier who killed the IS militant used a McMillan TAC-50 sniper rifle, from an elevated position.
Its manufacturer says its effective firing range is 1,800 metres, around half the distance the Canadian sniper managed.
