Marine fish species such as grey wrasse Symphodus cinereus, common sole Solea solea, knout goby Mesogobius batrachocephalus and rusty blenny Parablennius sanguinolentus were studied for their parasitic isopods on the Sinop coast of the Black Sea. Two cymothoid species (Nerocila bivittata and Nerocila orbignyi) were identified. Nerocila bivittata was found on the body surface and fins of grey wrasse, common sole, knout goby, and N. orbignyi on the dorsal fin of rusty blenny. The prevalence and mean intensity values of each parasite species on fishes were calculated. Fish species mentioned above were all new hosts for N. bivittata and N. orbignyi in the Turkish coast of the Black sea.