The Waterton River flows northeast from the Waterton Lakes to merge with the Belly River north of Stand Off, Alberta. It is interrupted in its journey by the Waterton Reservoir.

The Waterton River's best fishing is inside Waterton Lakes National Park, where it connects Middle and Lower Waterton Lakes. The 2-km stretch contains cutthroat and rainbow trout and is open for angling year-round.

Paddlers put in at Waterton National Park for a (30 km 18 mi) Class I and II drift to Waterton Reservoir.

Access is from Provincial Highway 5, inside Waterton Lakes National Park.

From Alberta Highway 5, inside Waterton Lakes National Park, two unpaved roads lead east to the section of Waterton River linking the middle and lower lakes.

From Alberta Highway 5, inside Waterton Lakes National Park, two unpaved roads lead east to the section of Waterton River linking the middle and lower lakes.