The Night Hawk River begins at Austen Lake in the northwest of the
Unorganized West Part of Timiskaming District at an elevation of . Portions of the primary inflow of Austen Lake, the West Night Hawk River, as well as all of that river's source, West Night Hawk Lake, lie in the northeastern portion of the
Unorganized, North Part of
Sudbury District, Ontario, meaning that the Night Hawk River drainage basin is in three Ontario districts. The Night Hawk River flows northeast, passes over a small dam, turns north, and takes in the left tributary Little Night Hawk River arriving from Little Night Hawk Lake. It turns northeast again, takes in the right tributary East Night Hawk River arriving from East Night Hawk Lake, heads north, and flows into the city of
Timmins in Cochrane District. The river heads northwest, takes in the left tributary West Night Hawk River, then reaches its mouth at St. Peter Bay at the southern tip of Night Hawk Lake at an elevation of . ==Tributaries==