The Chloride and Fluoride are two key factors in any aquatic ecosystems. The present paper highlights the seasonal variations of Chloride and Fluoride in Tamiraparani River (West) from June 2011 to May 2013. Twelve stations were selected for the study. The study reveals that high Chloride of 1050 mg/l was found in S12, during the months of June to August 2012, low chloride of 10 mg/l was found in stations S4, S5 during December to February 2011-2012, March to May 2012. The Fluoride was found high in stations S4, S6 as 0.6mg/l during June to August September to November 2011and June to August, September to November 2012, March to May 2013 and low Fluoride of 0.1mg/l was found in stations S1, S2, S4-S12 during December to February 2011-2012 and March to May 2012. The Fluoride levels seem to be high in upper reaches and a decreasing trend is found towards estuary. In contrary, Chloride level was low in upper reaches and it increases at the upper reaches of estuary and was maximum in the last station (S12). However, higher Chloride level was found during South West monsoon seasons in all the station studied. The fluctuation in due to rain water influx is also discussed. The Chloride and Fluoride was found to be significantly correlated (r=0.8021) in the 7th degree polynomial fit and the relationship established and discussed.