The grey-cheeked mangabey is a dark monkey, looking in shape overall like a small, hairy baboon.

Its thick brown fur is almost black in its forest home, with a slightly rufus/golden mane around the neck.

The sexes are similar, with the males slightly larger than the females.

Some authors in the past have considered the species to be restricted to the forest canopy, however more recently habituated troops have been observed on the forest floor collecting food.

Their territories cover several square miles of forest, and can both overlap with other troops and shift over time.