The Coxs River rises in Gardiners Gap, within Ben Bullen State Forest, east of Cullen Bullen, and flows through the Megalong Valley and parts of the Greater Blue Mountains Area World Heritage Site including the Blue Mountains and Kanangra-Boyd national parks, heading generally south and then east, joined by fifteen tributaries including the Little, Jenolan, Kedumba, Kowmung, and Wollondilly rivers, before reaching its confluence with the Warragamba River to form Lake Burragorang.

To the Aboriginal peoples who lived in the area for thousands of years before white settlement, Coxs River was one of two corridors that could be used to cross the Blue Mountains, the other being the Bilpin Ridge, now the site of Bells Line of Road.

Testing carried out by researchers from the Blue Mountains Conservation Society showed that this part of the river had high levels of heavy metals including zinc, copper and manganese, 125 times more sulphate than surrounding streams and only 5% of the oxygen that fish need.

The Sydney Catchment Authority confirmed that the test was accurate, but said the water gets safer to drink in the lower river, approaching Warragamba Dam.

The Department of Environment and Climate Change stated that the contamination could be caused by Delta Electricity's Wallerawang Power Station reusing its water as a result of drought.

High arsenic levels were found down stream of the plant, although it was diluted further downstream and was not thought to pose a risk to humans.

[10] A range of leisure activities are accessible adjacent to the river, including the Katoomba to Mittagong Trail, the Six Foot Track and camping.