Giant bullfrogs are the largest amphibians found in southern Africa. In Gauteng males reach a snout-vent length of 245 mm and a mass of 1.4 kg. In contrast to most other frogs and toads, males are larger than the females. The head is very broad. Two large bony spines separated by a smaller spine project upwards from the lower jaw. Several prominent, interrupted skin ridges are present on the back. A spade-like inner metatarsal tubercle is present on each heel, and is used for digging (Minter et al. 2004).

In adults, the dorsum is dark olive-green, but may vary from brown to grey and even blue; short sections of the longitudinal skin ridges may be white or cream. In juveniles, a pale vertebral stripe is often present, contrasting sharply with the bright green ground colour. The abdomen is white to creamy-yellow, except in the region of the forelimbs, where it is bright yellow in breeding males. Dark mottling may be present in the gular region of males (Du Preez 1996)