Several types of health problems in Jhajjar district of Haryana state are prevailing owing to groundwater quality problems such as high concentration of fluoride, chloride, salinity, TDS, etc. The objective of this work was to assess the overall groundwater quality of the district based on Water Quality Index (WQI), and find out the factors leading to continuous deterioration in groundwater quality. The study demonstrates that groundwater quality of Jhajjar district is totally unsuitable for drinking purposes and is directly or indirectly influenced by geogenic factors. About 60–70% of the samples analysed show high fluoride content. Other parameters such as hardness, electrical conductivity, Total Dissolved Solids (TDS), and Chloride are also above the permissible limits. Hydrogeologically the study area belongs to Indo-Gangetic alluvial plains, which are dominated by clay-silt, clay and grey micaceous sand formations. Clay rich formations are rich in fluorine and other salts and their weathering is most probably causing the continuous escalation in the fluoride and salinity concentration in groundwater. Several in-situ and ex-situ measures have been suggested for remediation and to prevent further escalation of water quality problems that are needed imperatively for the sustainable development of water resources.