Gonystylus affinis grows as a tree up to 50 metres (160 ft) tall, with a trunk diameter of up to 80 centimetres (31 in). Bark is reddish brown. Fruit is reddish brown, up to 5 centimetres (2.0 in) in diameter. Habitat is lowland forests from sea-level to 300 metres (1,000 ft) altitude. G. affinis is found in Peninsular Malaysia and Borneo.