The Cayoosh Range is defined by the valley of Cayoosh Creek on the south, which is followed by the Duffey Lake Road section of Highway 99, from Pemberton-Mount Currie to Lillooet, which are at the respective western and eastern ends of the range.

Cayoosh Pass, between the head of Duffey Lake and the descent to the Pemberton Valley at Lillooet Lake, was first traversed by a non-native by Sapper James Duffey of the Royal Engineers in 1860, who investigated (then dismissed it) as a possible overland alternative to the Douglas Road.

The western part of the range is coastal-alpine in character, with small glaciers and heavy snowfall.

The eastern, higher part of the range verges on the semi-arid climate typical of the Fraser Canyon and the rest of the Interior and has no permanent snowfields or ice, and is known for its beautiful alpine meadows and stunning vistas of the surrounding ranges to the north, south and east.

The second-highest peak in the Cayoosh Range is Mount Marriott at 2,735 m (8,973 ft), due south of D'Arcy (N'quatqua); it is not named for the hotel-empire family of the same name but for an RCAF officer who was killed in action in World War II.