In the present study 800 well water samples were collected from five Grama Niladhari (GN) divisions situated in Maharagama, Sri Lanka. The area is highly populated and urbanized with a very shallow ground water table. Ground water quality was analyzed and compared with different GN divisions identifying well water contamination pattern using Principal Component Analysis (PCA). Eighty wells were sampled monthly using simple random sampling method from January 2012 to October 2012. PCA analysis identified three clusters, Navinna GN division as cluster 1' with high electrical conductivity values, Jambugasmulla, Wijerama and Gangodawila South B together as ‘cluster 2' with high organic pollution and Wattegedara being the highest polluted GN division as ‘cluster 3'. Overall results indicated that water quality of the area is deteriorated with risk of potential water borne diseases and all parameters tested were far above the SriLanka Standard Institute standards given for drinking water quality.