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

The river begins at Nemegos Lake in geographic Halsey Township,[4] Sudbury District, and flows northeast under the Canadian Pacific Railway transcontinental railway main line at the community of Nemegos, location of the Nemegos railway station served by the Via Rail Sudbury–White River train.

[7] The river loops west then east through geographic Borden Township[8] back to Gamey township then goes north into geographic Chewett Township,[9] flows under Ontario Highway 101, then heads northwest to Nemegosenda Lake, where it takes in the left tributary Borden River.

The river leaves the lake from geographic Collins Township[10] at the north and heads north; the Chapleau-Nemegosenda River Provincial Park, operated by Ontario Parks, begins just north of the outflow from the lake.

[3] The river enters geographic Kapuskasing Township[16] in Algoma District, and flows under the Canadian National Railway transcontinental railway main line, between the railway points of Elsas to the west and Oatland to the east; the line is served at Elsas railway station by Via Rail transcontinental Canadian trains.