[1] It is part of the Great Lakes Basin, and is a right tributary of the Severn River.

It continues southwest into Minden Hills, Haliburton County, then back into Muskoka District in the municipality of Bracebridge, passes under Ontario Highway 118 and flows by the community of Vankoughnet, and enters the city of Kawartha Lakes.

The river turns west, flows over the Ragged Rapids, exits Kawartha Lakes, briefly forms the border between Simcoe County and Muskoka District, flows through the Big Eddy, then reaches the community of Cooper's Falls in the municipality of Ramara, Simcoe County.

It is a common misconception that the Black River flows into Lake Couchiching.

This was a problem for lumbermen in the 1860s, who established the Rama Timber Transport Company, to move logs from the Black River to Lake Couchiching.