Isopods are terrestrial crustaceans and live in moist soil; a few investigations take place regarding the terrestrial isopod fauna in Iran. The field work study was carried out at different humid areas of Arak city during May to November 2012. In this study a total of 100 individual Isopods were identified, some of them are belonging to genus Protracheoniscus (Verhoeff, 1917), one of the species was recognized to be closely related to Protracheoniscus major (Dollfus, 1903). P. major differentiated from the other species by the unique shape of male Fleopod-Endopodite I. This is the first report of Protracheoniscus major (Dollfus, 1903), from Iran.
