It is a fairly large species at 58 cm (23 in) in length, being by some margin the largest bittern in the genus Ixobrychus. Compared to related species, it has a longish neck and long yellow bill. The adult is uniformly black above, with yellow neck sides. It is whitish below, heavily streaked with brown. The juvenile is like the adult, but dark brown rather than black. They can be difficult to see, given their skulking lifestyle and reed bed habitat, but tend to fly fairly frequently when the all black upperparts makes them unmistakable.
Their breeding habitat is reed beds. They nest on platforms of reeds in shrubs, or sometimes in trees. Three to five eggs are laid.
