Most local people in the agricultural areas of Sistan and Baluchestan Province (Iran), generally consume shallow groundwater from farm wells. This study aimed to assess the water quality and health risk potentially of As, Pb, Cr and Ni for drinking purposes in Zarabad aquifer. Also the geochemical processes controlling chemistry of Zarabad aquifer were studied. Piper diagram shows two major hydrochemical facies of Na-Cl/SO₄ and Na-SO₄/Cl in the groundwater samples. Based on hydrogeochemical results (Composite and Gibbs diagrams), chemistry of groundwater is influenced by water-rock interaction, evaporation and ion exchange. Arsenic, Ni and Pb for 27, 53 and 80% of the groundwater samples show higher concentrations than the maximum acceptable limit for drinking water. According to the WQI values all of the water samples were considered unsuitable for drinking purpose. The results of principal component analysis (PCA) indicate that As, Ni, Pb and Cr have more influence from anthropogenic sources such as application of fertilizers and pesticides in the agricultural lands. The result of health risk assessment shows that the consumption of heavy metals (such as As and Pb) contaminated groundwater poses an emerging health threat to the populations in the study area, and hence needs regular monitoring and management measures.