Usually a true liana without tendrils, occasionally a scrambling shrub. Stems and branches often with triangular corky knobs; latex white. Leaves opposite, elliptic or ovate, up to 13.5 × 6.5 cm, dark green above much paler below with 3-8 pairs of lateral veins, hairless. Flowers normally appearing after the leaves, 1-3 per inflorescence. Corolla white and red, streaked with purple; lobes ovate, tapering to a point but without long linear tails. Fruit in 2 widely diverging follicles, sometimes at an angle of more than 180°, each 12-26 cm long, 3-4.5 cm wide, dark grey to purple-black, hairless, covered in lenticels.
When not in flower this species is virtually indistinguishable from Strophanthus petersianus. In that species the lenticels are very dense on the branches while in S. courmontii they are normally sparse to somewhat dense. The reverse is true for the lenticels on the follicles.