Presently, Sri Lankan coastal groundwater resources is threatened due to various anthropogenic activities and becoming a vulnerable source of water in the country. Northwestern coastal area of the country is characterized by unconfined sandy aquifers such as Kalpitiya Peninsula and Mannar Island. This study focuses on application of GIS and remote sensing techniques in assessing the present situation of coastal groundwater with reference to Kalpitiya Peninsula and Mannar Island in view of introducing a suitable monitoring and management plan for conservation of coastal groundwater. Thirteen hydrogeochemical parameters of 150 locations in both Kalpitiya and Mannar areas were analyzed for the samples both collected from dug wells and shallow tube wells in September, 2013. Groundwater Quality Index, Sodium Absorption Ratio, Soluble Sodium Percentage and DRASTIC methods were used to infer the groundwater vulnerability and resistivity imaging technique were also applied to access the groundwater contamination due to seawater intrusion. GIS was applied to integrate and analyze the spatial data obtained from the above techniques. This unconfined coastal sandy aquifer system which is highly specific and productive is a very good freshwater storage and can be considered as a national heritage of the country. Its inherent characters quite dissimilar to the other coastal aquifers can help us infer the potential of easy contamination and vulnerability. Since the Kalpitiya Peninsula (and Mannar Island in future) is subjected to intense vegetable cultivations, groundwater based irrigation and fertilizer applications, groundwater is at risk and already contaminated with regard to few chemical parameters. Thus, an immediate attention is needed for the future sake of existence of those fresh groundwater storages. Remediation measures for Kalpitiya and sound planning for Mannar Island is a must. Understanding the present situation with the application of GIS and remote sensing techniques favours effective data handling and utilization.