Groundbreaking studies of phlebotomine sand fly populations in Assis Brasil, State of Acre, Brazil, resulted in the collection of 13 new records of phlebotomine sand flies and one previously undescribed species. Lutzomyia naiffi sp. nov. is described here. The new species is similar to Lutzomyia columbiana (Ristorcelli & Van Ty) in measurements and other morphological characters.