Combining morphological and molecular data in an integrative approach, three new mayfly species of Epeorus ( Caucasiron ) are described. These include Epeorus ( Caucasiron ) alborzicus Hrivniak & Sroka, sp. nov. and Epeorus ( Caucasiron ) shargi Hrivniak & Sroka, sp. nov. from northern Iran, and Epeorus ( Caucasiron ) zagrosicus Hrivniak & Sroka, sp. nov. from central Iran. They are unambiguously delimited using both distance-based and likelihood-based approaches in the analyses of barcode COI sequences. Each new species is compared with other species of the subgenus and morphological diagnostic characters are provided. Based on extensive sampling of streams throughout the country, the distribution and habitat preferences of all Caucasiron species in Iran are assessed. Altogether, there are now six species recorded, among them also E. ( C. ) nigripilosus Sinitshenkova, 1976 is reported for the first time in Iran. Five species are distributed in the Alborz Mts. in northern Iran, one species was found in the Zagros Mts. in central Iran.