The White-breasted Waterhen has mainly dark slate-grey upperparts and flanks, and a white face, neck, breast and upper belly. The lower belly, vent and under-tail are rufous-chestnut coloured. Its body is flattened laterally to allow easier passage through reeds and undergrowth.

They have long toes, a short tail and yellow legs, as well as a pale yellowish bill with a red spot at the upper mandible's base.