The river begins at the Mossy River Dam at the north end of Dauphin Lake and flows north into the south end of Lake Winnipegosis at the community of Winnipegosis.

[3] In 1964, the Mossy River Dam was constructed at Terin's Landing at the outlet of Dauphin Lake to help regulate water levels.

The dam, which is operated by the province of Manitoba, is a ten bay concrete stoplog structure with a fish ladder.

From Fork River, Mossey River parallels Highway 20 (which is part of the Western Canadian Northern Woods and Water Route) until Winnipegosis at which point Highway 20 travels north then west while the river runs along the east side of the community before emptying into Lake Winnipegosis.

[6] Prior to arriving at Winnipegosis, Mossey River is crossed by PR 364 and an historic steel pony truss bridge along Bridge St coming south out of Winnipegosis.