Water quality management is an important issue in the modern times. In this paper, the application of fuzzy set theory for decision making in the assessment of groundwater quality for drinking purposes . This is illustrated with thirty groundwater samples collected from Ariyamangalam zone of Tiruchirappalli, S.India. These 30 samples were analyzed for 10 physiochemical parameters. This fuzzy groundwater quality model approach, the groundwater quality is classified in three categories,(1) just four samples comes in the desirable class certainty level of minimum 8% and a maximum of 79%.(2) 14 samples were classified in the acceptable category for drinking purpose with the maximum certainty level of 50%.(3) Rest of the 13 sample were in not acceptable class with a maximum certainty level of 100%. This approach is capable of showing the water quality assessment for drinking .