Abstract: Present work was designed to study the water quality of Thazhakkara segment of Achenkovil River based on physico-chemical, entomological and microbiological aspect following Water Quality Index and Family Biotic Index of aquatic insects. Sampling was done during summer season 2012. Three study sites were selected from the study segment as Vazhuvadi, Pottamelkadavu and Kunnam. Physico-chemical parameters like TDS (Total Dissolved Solids), Conductivity, Salinity, PH, Temperature, Turbidity, Dissolved Oxygen, BOD, Nitrate, Phosphate were analyzed. Mean with standard deviation and ANOVA were taken. Water Quality Index was also analyzed. It has been observed that overall water quality index of Thazhkkara segment of river Achenkovil during summer season was 53, that is some of the parameters substantially exceeded the limit. Microbiological analysis showed that the level of fecal coli form was moderate during summer season. An average of 7.9 Family biotic index of aquatic insects were obtained during the study period. The results showed that the Achenkovil river water at Thazhkkara segment was polluted with numerous organic pollutants.