The species M. melini has been observed in both the Pampa and Spinal ecoregions of Argentina. Researchers have underscored that distinguishing M. melini from other species within the same genus relies primarily on craniometric and molecular analyses. Morphological measurements alone do not offer a clear differentiation between M. melini and other members of this genus. This study aims to document the presence of M. melini within the Brazilian ecoregion, focusing on its morphological, morphometric and genetic characteristics. By undertaking a comprehensive examination, we seek to contribute valuable insights into the distribution and differentiation of M. melini in this region. Molossus melini specimens exhibited a forearm length ranging from 39.9 to 40.08 mm. The average intraspecific divergence was 1.2%, with specimens from the Argentine Pampas clustering in the same clade with a 98% bootstrap support and a posterior probability of: Regarding dorsal colouration, the specimens displayed fur with two bands—a Snow White base colour and apex colours ranging from Olive Brown, Broccoli Brown, Wood Brown to Yellowish-Brown. This marks the first record of M. melini in Brazil, expanding its distribution 1,300 km northeastwards into the Curitiba, Paraná, Atlantic Forest Ecoregion. The findings contribute valuable information on the distribution, morphology, morphometrics and genetics of this species.