8 - 9 cm. 3.2 - 4 g. Broad white line behind the eye. Nape and upperparts green, feathers that cover uppertail with reddish borders. Crown dull green. Tail squared. Males and females are different. Male: Bill red tipped black. Forehead and sides of head black. Back green. Throat bright green, rest of underparts cinnamon; flanks with green marks. Tail feathers reddish-cinnamon, central feathers with green borders. Female: Upper mandible black, lower red. Sides of head dark. Throat and underparts pale cinnamon. Outer tail feathers dark reddish with pale tip, inner feathers green. Immatures are similar to females but with green tinges on throat.

It was considered within Hylocharis leucotis for a long time, but this species is much greener and shows the pattern of the head most marked in males, moreover the restricted distribution of H. xantusii makes it unmistakably.