Pentanisia angustifolia leaves are sessile or stalkless, usually also hairless. The leaf-shape is narrowly lanceolate and long with an acutely pointed tip. The leaves become from 1 cm to 10 cm long.

The shape of the leaves distinguishes this plant from another species, P. prunelloides with similar flowers, found in parts of the same habitat. The latter species has broader, hairy leaves.

South Africa has three Pentanisia species; the other 12 completing the genus grow in Africa (Van Wyk and Malan, 1997; Manning, 2009).