Polychaete assemblages are relatively poorly known in comparison to other components from Indian waters. In the present study, the spatial and seasonal distributions of polychaetes were investigated in the Thondi coastal area. Polychaete assemblage structure seems to be influenced by environmental parameters, such as temperature, salinity, pH, dissolved oxygen and total organic carbon. A total of 34 polychaete species were found, of which 26 species were in station I while 22 species in station II. There was a pronounced variation in diversity of polychaetes between the studied sites. Among the families maximum percentage of species constituted by Glyceridae (12%) and minimum Owenidae (4%) at station I and in station II, the Eunicidae (14%) was maximum and Pisinidae as (4%) minimum. The population density varied from 1456 to 2456 no m(-2) in station I; 2120 to 4424 in station II and diversity index varied from 1.96 to 2.48 in station I; 2.01 to 2.53 in station II. Species richness varied from 1.21 to 1.65 in station I; 1.36 to 1.69 in station II and evenness index varied from 0.9 to 0.97 in station I; 0.91 to 0.98 in station II. BIO-ENV analysis showed that salinity, TOC and temperature as the key variables in influencing the faunal distribution.