Members of the genusSphaeromyxaThelohan, 1892 have been reported from a wide variety of fish species worldwide. In the present study, specimens of rusty blenny,Parablennius sanguinolentus, collected from Sinop on the Turkish Black Sea coast were investigated for myxosporean parasites by using both conventional and molecular methods.Sphaeromyxa sevastopoliNaidenova1970was the only myxosporean parasite found in the gall bladder of host fishes. The morphology peculiarities of obtainedS. sevastopolispores are in good agreement with those of original description and the morphometric data overlapped in spore length and width but differed in polar capsule length and width; however, they were within the ranges previously reported from 18 host fish species. Moreover, in the present study, molecular analysis of the 18S rDNA gene ofS. sevastopoliisolate in ourP. sanguinolentusas well as isolates from shore rocklingGaidropsarus mediterraneusand knout gobyMesogobius batrachocephaluswhich were previously morphologically identified and reported by Okkay and ozer (Acta Zool Bulg 72(1):123-130,2020) was done for the first time and our threeS. sevastopoligenotypes were allocated to the "balbianii" group which is characterized by straight or slightly curved and fusiform or ovoid spores with ovoid polar capsules.