Ceratothoa oxyrrhynchaena Koelbel, 1878, an ectoparasitic isopod (Cymothoidae), has been recorded for the fi rst time in Turkish waters. The samples of Lithognathus mormyrus that hosted the isopod were collected with local fi shing gears in the port of Babakale in the Turkish part of the Aegean Sea in 2014. The paper aims to present the morphological characters of C. oxyrrhynchaena with photos and drawings of the Turkish samples. These parasites are also frequently reported in aquaculture, where they can cause serious damage. Although the occurrence of C. oxyrrhynchaena in the Mediterranean Sea is well known, it had not been reported from Turkey previously. The present paper aims to inspire more detailed taxonomic studies about and comparisons with the cymothoid faunas of the neighbouring Mediterranean countries.