The Nihoa Millerbird currently occurs as a small population on Nihoa Island as well as a small introduced population on Laysan Island. The Nihoa millerbird is a 13 cm reed-warbler, dark olive and olive brown above with grayish margins on feathers; wing and retrices chaetura drab; whitish below with some grayish olive wash on both sided; and buffy brown flanks. Bill thin, blackish; tarsus and toes blackish gray. Sexes similar, but females slightly smaller.