Considering itsimportance and lack of information on its genetic structure, in this study, population genetic structure and genetic diversity of the annular seabream Diplodusannularis (L.) in the Turkish Seas was determined using the partial sequence of mitochondrial DNA cytochrome b gene (997 bp). Localities where annularseabream samples collected were as follows: the eastern Mediterranean Sea (Adana), the western Mediterranean Sea (Antalya), the Aegean Sea (İzmir), theMarmara Sea (Canakkale and İstanbul), Mid-Black Sea (Sinop) and the Eastern Black Sea (Rize). The population genetic structure was estimated throughpairwise FST, analysis of molecular variance and phylogenetic analyses (NJ, MP, ML and BI). As a result the genetic variability was low among the populationbased on haplotype and nucleotide diversities of cytochrome b gene. However, phylogenetic analyses of the cyt b haplotypes showed up there are two possiblegenetic groups (the Aegean-Mediterranean and Marmara-Black Sea) suggesting that the presence of restricted migration at the Straits of Dardanelles, separatingthe Aegean and Marmara Seas.