Landolphia kirkii is a woody climbing plant, 18 to 30 m tall, with a solitary, coiled stem with bifurcating tendrils. Juvenile branches are silky and delicately covered with rusty-tomentose hairs. The bark has a reddish-brown hue, with white lenticels. The plant contains watery milky sap (latex). Leaves membranous to almost leathery (subcoriaceous), opposite, lanceolate to oblong, occasionally ovate to elliptic, 24-92 x 10-32 mm, upper surface shiny, smooth and dark green, lower surface light coloured (pale), 10-12 pairs of secondary veins clearly evident, apex attenuated, midrib channelled and prominent, petiole 2-7 mm.

Inflorescence a miniature pedunculate corymb creating compact clumps. Flowers small, ranging between 3 and 5 mm long, sweetly scented, whitish or creamy to yellow, in summer (Nov.-Jan.) Every flower bears two sepal-like bracteoles. Calyx is around 2 mm long, the sepals are broadly oblong or obtuse, greyish-brown, not shiny, ciliate, puberulent, and have a hispid midrib. Corolla is white, cream-coloured, or yellow, corolla tube lengthranges between3.5 and 4.5 mm, broader apex with a thinner base, corolla lobes 4 mm long, narrowly elliptic, equivalent to the tube, smooth. External surface covered with fine hairs, particularly over the calyx. Stamens are positioned over the centre of the corolla tube; anthers subsessile, less than 1 mm long. Ovary ranges between 0.75-1 mm in length, smooth, ovoid; ovules innumerable; stigma ranges between 1-1.5 mm in length, located below the anthers; style columnar less than 1 mm in length. Fruit is edible, globose to pear-shaped, between 80-150 mm in diameter, with a thin woody shell, skin is green, pale orange when ripe, and flesh is white.  Fruits are borne in late summer, autumn and winter (Mar.-Jul.). Seeds are several, distinctly compacted and submerged in a tangled pulp, measuring between 11-14 mm in length; cotyledons are slim, and the endosperm is slippery.