In a sample of 15 individuals, weights ranged between 600 and 3,250 g (1.32 and 7.17 lb), and snout-vent lengths were between 17 and 32 cm (6.7 and 12.6 in). Their eyes can be nearly 2.5 cm (0.98 in) in diameter. The conspicuous tympanum has a diameter of about 0.5 cm (0.20 in) and is separated from the eye by about 5 cm (2.0 in) in adults. The next largest extant anurans are the cane toad, about a third smaller than the goliath in the largest specimens, and the African bullfrog, which is just over half the size of the goliath. Goliath frog eggs and tadpoles are about the same size as other frogs despite its very large adult form.
A lateral fold extends from the eye to the posterior portion of the tympanum. Toes are fully webbed, with large interdigital membranes extending down to the toe tips. The second toe is the longest. The skin on the dorsum and on top of the limbs is granular. Dorsal coloration is green sienna, while the abdomen and ventral part of the limbs are yellow/orange. They have acute hearing but no vocal sac, and also lack nuptial pads.