Gonystylus brunnescens grows as a tree up to 40 metres (130 ft) tall, with a trunk diameter of up to 100 centimetres (40 in). Bark is reddish to dark brown. Fruit is round, brown, up to 7 centimetres (2.8 in) in diameter. The specific epithet brunnescens is from the Latin meaning "brownish". Its habitat is forest from 40 to 1,500 metres (130 to 4,920 ft) altitude. G. brunnescens is found in Peninsular Malaysia and Borneo.