The main aim of the paper was to assess the groundwater quality near the Municipal Solid Waste Landfill (MSW) landfill sites using landfill water pollution index (LWPI), Nemerow index (PI) and chemometric expertise. For this purpose, an analysis of eleven physicochemical parameters was performed including: pH, electrolytic conductivity (EC), total suspension (TS), chemical oxygen demand (COD), biochemical oxygen demand (BOD5), total organic carbon (TOC), dissolved organic carbon (DOC), total nitrogen (TN), total dissolved nitrogen (DN), total phosphorus (TP) and orthophosphates (OP) in landfill leachates and groundwater samples from two different MSW landfill sites in NE Poland. Research materials were collected in the period from January 2016 to May 2017. More than 80% of the data variance was explained by two factors identified by the use of principal component analysis: 44.8% was explained by the factor contributed by carbon and nitrogen-related parameters, while 35.7% by the factor contributed by phosphorus-related parameters and both, chemical and biochemical oxygen demands. The obtained results indicated negative impact of MSW landfill sites on groundwater quality which was clearly observed for samples from P1 and P4 in landfill H and for samples from P3 in landfill U.