Hydrochemical characterization of groundwater quality in Nkalagu District, southeastern Nigeria was carried to determine the main factors controlling the chemistry of groundwater and its suitability for drinking and irrigation purposes. Sixty (60) groundwater samples collected from boreholes and hand-dug wells in different parts of the area were analyzed for a range of physiochemical parameters and heavy metal constituents. The results show that concentration of the major ions were in the order Cl->HCO3->SO42->NO3- and Na>Ca2+>Mg2+>K+. The groundwater samples are slightly acidic with pH of 5.28 to 8.04; moderately hard with TH of 112.88 to 467.78 mg/l. The district is mainly controlled by carbonate and silicate mineral weathering based on the available result. Three main flow regimes were identified with Q-mode cluster analysis. Based on the WQIanalysis results, the groundwater quality in the district was classified, generally as ‘poor’ to ‘excellent’ for drinking purpose. Groundwater quality for drinking purpose were noted to deteriorates as one move from west towards the east of the district, while the north and south part pf the study area indicated the best quality in the district. Groundwater quality for irrigation purpose showed excellent quality based on the United States Salinity Laboratory and Wilcox diagrams. For future use of groundwater resource in the district we recommend implementation rules and guidelines in the area to enhance health and preserve groundwater sources in the district.