Sterculia murex grows up to 6-12m with wide, with spreading branches and 1-2 m stems up to 30 cm in diameter. The stem is covered with thick, ribbed, gray-brown bark. In old wood, the bark becomes almost black and is cracked into rectangular segments.

The leaves are borne on long hairy stalks, and are composed of 5-10 stalkless leaflets radiating, finger-like from one point. They are oblong to widely lance-shaped, narrowed to both ends, pointed, usually up to 10 cm long and 5 cm wide. The leaves are velvety both sides, the midrib, secondary veins and the netted veins conspicuous on the lower surface.

Sterculia murex flowers in sprays at the ends of the usually bare branches from August to October. They are waxy and yellow, marked with brown or crimson flowers. As in all the Sterculias, the petals are absent while the sepals are petal-like.

The five-lobed fruits are unique in appearance. They are large (up to 30cm in diameter if all lobes develop), woody and covered thickly with hard spines. The shell contains large oval seeds, resting in a bed of stinging hairs that can be irritating on contact with the skin or eyes. It is seldom that a very big complete fruit is collected as they grow high on the tree and shatter as they fall.