Groundwater, a vital resource in Bangladesh for agriculture, domestic, and industrial use, faces a growing crisis due to contamination from both natural and human sources. This study aims to provide a comprehensive assessment of the nation’s groundwater quality using the widely recognized Canadian Council of Ministers of the Environment Water Quality Index (CCME WQI) model. The study utilized data of nine key water quality parameters including Temperature, pH, EC, TDS, Chloride, Sulphate, Nitrate, Iron, and Fluoride from 117 monitoring stations of Bangladesh Water Development Board (BWDB) during 2018–19. The findings revealed that Bangladesh’s groundwater is generally in fair condition, with a mean and median WQI scores of 75 and 76, respectively. Among the stations, 65 fall into the “Fair” category, 44 into the “Good” category, and none were classified as “Poor.” However, seven stations, mostly in the southwestern coastal region, showed “Marginal” quality due to factors like salinity intrusion. Statistical analysis revealed significant parameter relationships. Strong positive correlations were found among Electrical Conductivity (EC), Total Dissolved Solids (TDS), and Chloride. Furthermore, the WQI demonstrated a strong negative correlation with EC (−0.52), TDS (−0.51), and Iron (−0.50), identifying them as the most influential factors in water quality deterioration. These findings offer crucial insights for developing effective strategies for sustainable groundwater management and protection.