The species of the Isophya major-group (Orthoptera: Tettigoniidae: Phaneropterinae), are reviewed. I. major Brunner von Wattenwyl and I. mavromoustakisi Uvarov are redescribed. Two new species are described; Isophya mersinensis Sevgili & Çiplak sp. n. and Isophya salmani Sevgili & Heller sp. n. from south Anatolia. Illustrations of morphology and male calling song are provided and a detailed comparison of the four species in the group is presented. We conclude that these four species constitute a natural group in sharing male cerci with two or more denticles not ordered in a line, a character unique to this species group within the genus. From an evaluation of their morphology and song characteristics, relationships among the species in the group are I. major + (I. mersinensis sp. n. + (I. salmani + I. mavromoustakisi). Based on the the distribution pattern and habitat preference, we concluded that the division of I. salmani and I. mavromoustakisi was a vicariant event resulting from the separation of Cyprus and Anatolia due to reflooding of the Mediterranean after the Messinian salinity crisis at the beginning of the Pliocene, around 5 My ago.