Abstract: The present study deals with assessment of the water quality of the River Achencovil. Sabarimala is the largest annual pilgrimage in India with an estimated 45–50 million devotees visiting every year. The Achencovil River is a small river not more than 130 kilometers. Pilgrims use the water of Achencovil River for various sanitary purposes. The water quality is also disturbed by various other anthropogenic activities by the population living near the river. The microbiological and physico-chemical characteristics were studied and analyzed during July 2010 – April 2011 using standard procedures. The mid-stream part of the river is selected for the study. The results revealed that all the studied sites showed more pollution during the pilgrimage season (post monsoon) than the off seasons (monsoon and summer) and also showed fluctuations in microbiological and physico-chemical parameters. Pollution of river water can be reduced by providing proper sanitation facility to pilgrims and by providing proper methods for dumping of sewage and wastes. Almost all parameters showed significant (P<0.05) seasonal variation between segments and was determined by ANOVA.