This species is an all-year resident throughout most tropical and subtropical parts of the Indian Subcontinent to Southeast Asia and adjoining regions. The typical habitat of brown fish owls is forest and woodland bordering streams, lakes or rice fields. This species is a large owl, but it is intermediate in size between other fish owls. It has prominent ear tufts but as in all fish owls, their tufts hang to the side of the head and have a scraggly look. The upperparts are rufous brown and heavily streaked with black or dark brown. The underparts are buffy-fulvous to whitish, with wavy dark brown streaks and finer brown barring. The throat is white and can be conspicuously puffed, while the facial disk is indistinct. The irides are golden yellow, the feet a duller yellow, and the bill is dark. Sexes do not differ in appearance except for size.
It grabs food by gliding over the water, nearly skimming it with its feet and grabbing its prey by quickly extending its long legs. It feeds mainly on fishes, frogs and aquatic crustaceans. It usually selects the larger freshwater fish available in waterways. Compared to the tawny fish owl, which prefers flowing waters, brown fish owls frequently hunt in still or stagnant waters.