This study focuses on the analyses of the effects of solid waste landfill and their leachate on the groundwater quality in Banjaluka, Bosnia and Hercegovina. Leachates from municipal solid waste landfill contain a diversity of contaminants. Samples of landfill leachate and groundwater were analysed in order to evaluate the impact of leachate on groundwater quality from Banjaluka landfill. The leachate from Banjaluka landfill contains heavy metals, organic and inorganic compounds in its composition. Groundwater samples, which are under the influence of landfill, have higher values for heavy metals (Pb i Cd) than is proposed by the World Health Organization drinking water regulation and EU Directive on the quality of water intended for human consumption. The multivariate statistical methods, hierarchical cluster analysis and principal component analysis, were applied to groundwater and leachate physico-chemical data. Principal component analysis revealed two sources of pollution in the groundwater: first source is from natural/geochemical process in soil and groundwater and the second source of pollution is from landfill site and leachate. Hierarchical cluster analysis shows that one group represents the samples of groundwater under the influence of landfill while the second cluster represents samples of groundwater without impact of landfill site and leachate.