In this paper an attempt has been made to understand the groundwater suitability for irrigated agriculture in Marudaiyar sub-basin. The chemical aspects of groundwater in the study area, 32 control wells considered which are almost equally distributed throughout the study area. Geo-chemical data were analysed to understand the pH, Electrical Conductivity, Total Hardness, TDS and SAR in the study area. The plotted geochemical data in the USSL diagram indicates 34.37 per cent (in pre-monsoon) and 46.87 per cent (in post-monsoon) of water samples are of good category and most of these samples are of C3S1 type. The poor water quality category is 3.12 per cent in pre-monsoon and 6.25 per cent in post-monsoon. The assessment of groundwater quality for irrigated agriculture using Modified Piper’s trilinear diagram shows result similar to that from the USSL diagram.