[1] It is part of the James Bay drainage basin, and is a right tributary of the Abitibi River.

The river begins at an unnamed lake in geographic Morrisette Township[2] in the municipality of Kirkland Lake, Timiskaming District, just north of Kirkland Lake Airport, and heads north into geographic Bisley Township[3] in Cochrane District, then turns northwest, and enters geographic Melba Township[4] in the municipality of Black River-Matheson.

It takes in the left tributaries Little Black River and Whiteclay River, passes under Ontario Highway 572, takes in the right tributary Pike River, flows through the Black River Generating Station and dam, built in 1929,[5] and passes under Ontario Highway 101 at the community of Matheson.

From this point on, the original river course is flooded to the same elevation as the Iroquois Falls Generating Station[6] on the Abitibi River at Iroquois Falls downstream.

In Matheson-Black River, from the community of Wavell to the community of Matheson, both Ontario Highway 11 and the Ontario Northland Railway main line follow the river valley.