The sexes are about the same size, but they differ considerably in coloration; males are black-colored with remarkable white brows, while females have a grey-brown fur, which is darker at the chest and neck.

White rings around their eyes and mouths give their faces a mask-like appearance.

In northeast India, the hoolock is found south of Brahmaputra and the North Bank areas and east of the Dibang Rivers.

In China, in historical times, the skywalker gibbon was recorded in nine counties in the west bank of the Salween River in westernmost Yunnan province.

Based on more recent interview surveys conducted in October–November 2008 and field surveys conducted in Mar, Apr, and Aug 2009, the current Chinese population of hoolock gibbons was found to be restricted to three counties (Baoshan, Tengchong, and Yingjiang).

In Myanmar, all three species of hoolock gibbon can be found in the forested areas west of Thanlwin river.

Their calls serve to locate family members and ward off other gibbons from their territory.