In the revision of the Ceratopogonini of the World, Wirth & Grogan (1988) placed the species of the Monohelea multilineata group in the new genus Downeshelea, which includes 33 species (Borkent, 2011), most of them known from the New World. Borkent and Spinelli (2000, 2007) listed 18 species from the Neotropical Region and Felippe-Bauer and Silva (2008) subsequently described D. oliveirai Felippe-Bauer from northern Brazil. From Mexico, only D. multilineata (Lutz) and D. panamensis (Lane & Wirth) have been reported. The study of male specimens of Downeshelea from the state of Oaxaca, Veracruz and Quintana Roo revealed the presence of an undescribed species, and the presence of D. fluminensis Felippe-Bauer that has been reported for only the type locality, Rio de Janeiro, Brazil. The study of additional material from Belize and Colombia revealed that the new species also is present out of Mexico. In this paper, we describe and illustrate the new species, comparing it with related species of Neotropical Downeshelea, which now includes 20 species for this biogeographical region, of which four inhabit Mexico.