The aim of the present study was to describe the mollusk syntaxon associated with Cystoseira barbata and Mytilus galloprovincialis facies, which are widely distributed along the coasts of the Sinop Peninsula, Turkey. Four stations were chosen for each facies at depths of 0.5-5 m, and a total of 32 seasonal samplings were performed with 4 replicate groups between February 2006 and November 2006. As a result of the qualitative and quantitative analyses, the C. barbata facies was shown to be represented by 14 species and 5807 specimens, whereas that of M. galloprovincialis was represented by 11 species and 18,407 specimens. Dominant species of the C. barbata facies were Mytilaster lineatus (56%), Tricolia pullus (18%), Rissoa splendida (12%), and Gibbula adansonii (7%). Dominant species of the M. galloprovincialis facies were, however, Mytilaster lineatus (63%) and Mytilus galloprovincialis (36%). Seasonal water parameters were also measured at the stations. Seasonal and spatial variations in the mollusk fauna were observed and showed the highest values in station 3 and during the summer period.