Groundwater contamination is a significant threat to water security in Bangladesh, especially in coastal areas influenced by salinity intrusion and geogenic pollutants. The study has collected 48 groundwater samples and analyzed 16 water quality parameters to assess the suitability of groundwater for drinking and irrigation purposes in a highly vulnerable coastal area of Bangladesh. The Canadian Council of Ministers of the Environment Water Quality Index (CCME WQI), Metal Index (MI), and Heavy Metal Pollution Index (HPI) were used to assess drinking water quality. In contrast, irrigation water suitability was evaluated using indices like Sodium Absorption Ratio (SAR), Sodium Percentage (Na%), Magnesium Absorption Ratio (MAR), and Kelly Ratio (KR). The results show that 72.92 % of the samples were above WHO drinking water guidelines for EC, which indicated high salinity risks. The CCME WQI classified 25 % of the samples as marginal or poor, and MI and HPI both showed significant contamination, mainly due to high Fe and As concentrations. The MAR indicated that 25 % of the samples were unsuitable for irrigation, mainly because of high salinity and sodium. Spatial analysis proved that severe deterioration of groundwater quality has been taking place in the southern area of Pirojpur severely, which requires urgent intervention, and continuous monitoring for safeguarding water resources in this vulnerable area.