The Sri Lanka frogmouth is about 23 cm long. It looks large-headed and has a large flattened hooked bill and a huge frog-like gape. The female is rufous, lightly spotted with white. The male is grey and more heavily spotted.

Like other frogmouths, this species rests upright on branches during the day, camouflaged by its cryptic plumage and appearing like a broken branch. At night, it hunts insects with its large gape. The flight appears weak and fluttery, but they are capable of flying quietly under the forest canopy.