This is a distinctive wagtail, the only one placed in the genus Dendronanthus (all other wagtails are placed in Motacilla). The forest wagtail is 18 cm in length, a slender bird with a long tail. The back and crown are olive brown, and the wings are black with two yellow wing bars and white tertial edges. There is a white supercilium, above a dark stripe through the eye. The underparts are white, apart from a black double breast band. The upper breast band is bib-like while the lower band is often broken. Sexes are similar. Young birds are more yellowish on the underside.