Landfilling remains one of the predominant municipal solid waste disposal methods in the world, however, improperly designed landfills pose severe threats to the surrounding aquatic systems through the leaching of toxic chemicals. This study investigated heavy metals (HMs)- cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), zinc (Zn) and a metalloid; arsenic (As) in surface and groundwater (25 samples each) around a landfill site in Khanewal District located in Central Punjab. The HMs were analyzed using Flame Atomic Absorption Spectrometer (FAAS) while As was analyzed using Hydride Generation AAS. Results obtained indicated that the mean concentrations of As, Cd, and Pb in both surface (0.05,0.009,0.13) mg/l and groundwater (0.029, 0.03, 0.04) mg/l exceeded the World Health Organization (WHO) permissible limits. The correlation, cluster analysis, and principal component analysis (PCA) all showed high positive relationships between most metals. According to the heavy metal pollution index, the groundwater quality classified as poor to unsuitable due to elevated concentrations of Cd, Cu, Pb, Zn, and As. Health Risk Assessments (HQ>1) revealed significant non-carcinogenic risks associated with Cd and As exposure through drinking groundwater. Collectively, these findings highlight the urgent need to strengthen municipal solid waste management through engineered landfill design, effective leachate collection and treatment, continuous groundwater quality monitoring, and risk-based remediation strategies to mitigate landfill-derived heavy metal contamination, protect drinking water resources, and reduce potential human health risks.