[3] It flows from headwaters near Lower Ugashik Lake and empties into Ugashik Bay, an estuary of the Bering Sea's Bristol Bay.

[1] The origin of the name Ugashik is somewhat obscure, although early spelling variants such as Oogashik and Ougashick suggest the name pertains to the source of the river: two waters (lakes) and its muddy character.

The river is navigable to a small lagoon located just outside the outlet from Lower Ugashik Lake.

A small rapids between the lake and the lagoon serves as the location of a seasonally staffed salmon-counting weir operated by the Alaska Department of Fish and Game.

The river hosts several seasonal salmon runs including, during the peak summer season, part of the largest sockeye salmon migration in the world.