The soft bottom polychaete community was examined seasonally at eight stations between August 2009 and July 2010. A total of 76 species belonging to 27 families were identified in the Sinop Peninsula (southern Black Sea), of which 23 species are new records for the Black Sea fauna and 7 species for the Black Sea coast of Turkey. Syllidae was the best represented family in the research area and contributed 15.78% of the total fauna. The most dominant and frequent species were Micronephthys stammeri and Protodorvillea kefersteini in the study area. Community parameters varied significantly among stations and seasons; number of species ranged from 1 to 21 per 400 cm(2), density from 25 to 16,700 ind. m(-2), Shannon-Wiener diversity index value from 0 to 3.4, and Pielou evenness index value from 0 to 0.98. The highest population density was recorded at station C1 in winter, where P. kefersteini was the most dominant species (15,125 ind. m(-2)). The correlation between polychaete community and environmental variables was strongly high (r = 0.91) according to canonical correlation analysis. The main factors affecting the polychaete assemblages were depth and sediment texture.