A new cave isopod species of the genus Stenasellus Dollfus, 1897 (Stenasellidae) from Iran is reported and described. The new species, Stenasellus tashanensis sp. n. was found in Tashan Cave (Khuzestan province, southwest Iran). A complete description and drawings of the new species are provided. This new species is morphologically close to S. vermeuleni Magniez & Stock, 2000 from Oman.