This is a mottled brown duck with white and green flashes on its wings. The male and female Sunda Teal share the same colouration, in contrast to the related Chestnut Teal, whose male and female are strikingly different. The nominate Sunda Teal has almost identical colouration to the female Chestnut Teal and can only be distinguished by its lighter coloured neck, paler face and especially the bulging forehead. The Andaman Teal has a variable amount of white on the forehead and around the eyes. The Rennell Island Teal looked like a smaller version of the nominate subspecies, with a stubbier bill. Juveniles are paler than adults, especially on the head.
The Sunda Teal nests near its favoured freshwater lakes and marshes, usually on the ground, but also in tree holes or rabbit burrows.
This is a vocal duck, especially at night. The male gives a soft preep, and the female has a loud quack.
Two subspecies are extant, and one extinct:
The Grey Teal, Anas gracilis was formerly considered to belong into this species.