Apolemichthys xanthurus has a body with a cream background colour with a network of dark lines on the scales creating a lattice pattern over this. The edges of the body are a solid dark colour. The
caudal fin is bright yellow while the
dorsal and
anal fins are black with a white margin. Like the closely related
Apolemichthys xanthotis this species has a yellow spot on the upper preoperculum but the black on the head does not extend as far as this spot, contrasting less with its background. The juveniles have a wide black band running over the eye and an oblique area of black on the back, this patch fades as the fish matures. The dorsal fin contains 14 spines and 17–19 soft rays while the anal fin has 3 spines and 17–18 soft rays. This species attains a maximum total length of . ==Distribution==