The specific epithet macrocarpa is from the Greek meaning "large fruit".

[3] Mastixia macrocarpa grows as a tree measuring up to 20 metres (70 ft) tall with a trunk diameter of up to 20 centimetres (8 in).

The pale green fruits are oblong-ovoid and measure up to 4 cm (2 in) long.

[3] Mastixia macrocarpa grows naturally in Malaysia's Sarawak state and the Philippines' Luzon island.

Its habitat is mixed dipterocarp forests at around 75 metres (200 ft) altitude.