Seasonal dissimilarity study of hydro–chemical analysis in Pazhayar River, Tamilnadu was carried out in June– July(dry) till October–November(wet) 2014.The river water quality was studied at three selected stations namely Boothapandi (S1), Thuckalai (S2) and Kuzhithurai (S3) to signify unlike localities with changeable anthropogenic discharge. The in–situ water quality and hydro–chemical parameters of the samples were measured for pH, temperature, electrical conductivity (EC), total alkalinity (TALK), total dissolved solids (TDS), dissolved oxygen (DO), salinity, Ammoniacal nitrogen (NH3–N), biochemical and chemical oxygen demand (BOD & COD), suspended solids (SS), nitrate and phosphate following standard methods and then compared with WHO standards. Bacteriological analyses were also carried out for the same period of time. Introduction of sewage into the river plays a noteworthy responsibility for bacterial contamination. The results indicate that some sort of integrated river water management and good agriculture practice scheme should be implemented.