The Inuit village and region's administrative centre Kuujjuaq lies on the shores of the Koksoak, about 50 kilometres (31 mi) south from its mouth.

The name Koksoak is believed to originate from Moravian missionaries who evangelized among the Inuit of the area at the beginning of British rule and incorrectly spelled the Inuktitut word Kuujjuaq, meaning "great river."

Most of the flow occurs during the early summer when the ice on the river thaws and snow in the Canadian Shield melts.

The Koksoak River lies on the boundary between the northern limit of the boreal forest and the vast tundra expanses of the Ungava Peninsula to the north.

All the Koksoak basin is covered with permafrost - discontinuous in the south and continuous in the north.