Mallotus pleiogynus is an
evergreen tree growing up to tall, with a
trunk diameter of up to . The outer bark is brown to grey in colour and smooth, with white to yellow inner bark. The papery leaves are ovate in shape with a pointed tip and rounded base, measuring by . There are 2-4 large, dark brown
nectaries at the base of each leaf on the upper surface. The undersides of the leaves are densely hairy.
M. pleiogynus is
dioecious and the
inflorescences are
racemes, produced singly or less commonly in a pair. Male plants produce inflorescences up to long, with dark coloured flowers measuring in diameter and composed of 3-4 pointed
sepals surrounding a cluster of 15-50
stamens. Female plants produce inflorescences up to long, each flower measuring in diameter and bearing 4-6 sepals and several plumose
stigmas. The fruits are ellipsoid
indehiscent drupes measuring by . The exterior of the fruit is hairy and somewhat wrinkled, yellow to orange when fresh when fresh, turning yellowish to reddish brown and developing 7-9 distinct longitudinal ridges when dry. ==References==