A base line study involving analysis of groundwater samples from the Ghriss Plain Plio-quaternary aquifer, in northwest Algeria, was carried out to determine the major elements chemistry and to assess the hydrogeochemical processes and water quality for domestic use. The main groundwater facies in the area belong to the Mg–HCO3 and Mg–Cl types. Based on TDS classification, 44.5% of the analyzed samples belong to fresh water and the remaining 55.5% to brackish water categories. A comparison of groundwater quality parameters in relation to WHO limits for drinking water shows that the concentrations of TDS, Cl− and NO3− exceed the desirable limits in many water samples. The principal component analysis (PCA) technique reveals the contribution of Cl−, Na+, Ca2+, K+ and Mg2+ in the salinization process and underlines the contamination of the groundwater with NO3− in relation to the widespread application of nitrate fertilizers and/or infiltration of untreated urban wastewater. The groundwater quality index (GWQI) shows that 70.5% of the water samples fall within the excellent-to-good category, whereas the remaining samples fall in the poor-to-unsuitable for drinking category.