Grewia robusta is a multi-stemmed shrub or small tree, up to 3 m high. Its bark is often spiny, and grey. Older stems are roundish. The leaves are often clustered on abbreviated side-shoots, broadly elliptic to ovate or almost round, 13-25 x 10-20 mm. They are 3-veined from the base, leathery, shiny dark green above, rather paler greyish green below, with short hairs; apex broadly tapering; base rounded, sometimes lobed, almost symmetric; margins have been described as bluntly toothed to scalloped or almost entire, glossy dark green above, pale greyish green and with short hairs below. The petiole (leaf stalk) is very short.

The flowers are small, bright pink and sweetly scented They are solitary, up to 25 mm in diameter, leaf-opposed, with stamens in a central mass. The flowering time is August-December. The fruits are round and fleshy drupes (fruits such as plums), reddish brown and entire to deeply 2- to 4-lobed, up to 20 mm in diameter.