The Caatinga-endemic nectar-feeding bat, Xeronycteris vieirai Gregorin & Ditchfield, 2005 was described based on four specimens. Since then, only two additional specimens have been reported in the literature. Examination of a new specimen that closely agrees with the original description but presents two additional upper premolars, led us to review the type series of this taxon. Our analysis provided support to the recognition of the new specimen as a X. vieirai with supernumerary teeth and revealed new diagnostic characters that can help in the field identification of this species. Xeronycteris vieirai presents tricolored dorsal fur, entirely naked forearm, connection of the base of the spear of the noseleaf with the upper limit of the horseshoe with a marked ridge, and chin with simple dermal pads and a relatively slight cleft. Additional new characters described here include anterior zygomatic arches reduced and not extending laterally and upward with respect to upper toothrow, basioccipital pits deep and separated by a high and thin bone septum, and mandible with a pronounced ridge at anterior symphysis. We propose an emended diagnosis based on morphological characters and provide a rectification on the original notation related to the holotype.