Abstarct: In Fariman-Torbat Jam plain, groundwater is the most important water resource for drinking, agriculture and industry useage. In this study, factors affecting the quality of groundwater in Fariman-Torbat Jam plain have been investigated. For this purpose, twenty-six groundwater samples were collected. Major ion concentration, nitrate content, TDS value, and potentially toxic elements concentrations were determined using standard methods. The mean concentrations of sodium, calcium, magnesium and potassium in the water samples were 250.3, 53.2, 40.2 and 2.1 mg/liter, respectively. The average concentrations of bicarbonate, sulfate and chloride were 222.1, 321.7 and 220.3 mg/l, respectively. The average concentration of nitrate in the studied samples was 12.1 mg/l. The average concentrations of Pb, As and Cd were 33.9, 4.5, and 1.8 μg/l, respectively. The concentration of Pb in groundwater samples of Fariman-Torbat Jam plain is higher than the average concentration in fresh waters. However the concentration of Cd and As in most of the samples is less than the average concentration in fresh waters. Saturation index values showed that groundwater is in equilibrium with carbonate minerals (calcite, dolomite and aragonite). Also, the calculation of ion ratios indicated that evaporation and dissolution are two major processes in the aquifer. baxsed on the calculation of salinity index, most of the samples are placed in moderate salinity class. Wilcox plot also showed that most of the samples are classified as medium to high salinity waters; thus they are suitable for irrigation of products with moderate to high salinity tolerance. On the basis of the water quality index values, the quality of groundwater samples for drinking varied from suitable to very weak. Calculation of Langelier Index indicated that the samples are not suitable for industrial applications.