A new Neotropical species of Trentepohlia (Mongoma) is described from Cuba. This is the first species of the subgenus from the West Indies, whereas the other four Trentepohlia spp. are from the subgenus Paramongoma. Notes on the phenology of this new species are provided. Also, we discuss the transfer of Trentepohlia suberrans Alexander, 1979 to Mongoma and provide a key for the identification of the three species of this subgenus present in the Neotropics.