Sæther (1981) erected the genus Diplosmittia based on a species from Saint Lucia and Saint Vincent in the British West Indies. The genus was revised by Pinho et al. (2009). To date, the genus comprises ten species: Diplosmittia harrisoni Sæther, 1981; D. carinata Sæther, 1985; D. recisus Sæther, 1988; D. beluina Andersen, 1996; D. forficata Andersen, 1996; D. plaumanni Pinho, Mendes & Andersen, 2009; D. boraceia Pinho, Mendes & Andersen, 2009; D. aragua Pinho, Mendes & Andersen, 2009; D. cerayma Pinho, Mendes & Andersen, 2009; and D. caribensis Wiedenbrug & Silva, 2016. Diplosmittia sasai Makarchenko & Makarchenko, 2005 was placed as a synonym of Pseudosmittia mathildae Albu, 1968 by Makarchenko & Makarchenko (2008). Except for D. carinata from Michigan, U.S.A., all species are Neotropical and mostly recorded from the Caribbean and northern part of South America. During field work in a remote mountainous region in the Brazilian Amazon, a unique new species with the gonostylus split into three parts was collected and is described and figured below. In addition, new records of D. plaumanni are provided.