Canthium gilfillanii is a shrub or small tree growing from 2 m to 4,5 m in height (SA Tree List No. 706). The bark is pale grey and smooth, the young twigs covered in white hairs.
The opposite leaves grow on short petioles of about 2 mm, having triangular stipules at their stalk bases. Leaf shape is almost round to broadly ovate or elliptic; the leaf tip tapers broadly, the base is square or rounded. Leaf texture is soft and velvety from fine hairy coverings on both surfaces. Three or four pairs of lateral veins ascend to the margins from the midrib, the net-veining is obscure.
Small green, whitish or yellow flowers, faintly scented, appear in branched clusters at upper nodes during winter to early summer (Coates Palgrave, 2002).