This paper reports new geochemical data on dissolved major and minor constituents in surface waters and groundwater collected in the Gharye-Alarab basin (south-eastern Iran) and provides a preliminary characterization of the hydrogeochemical processes governing the natural water evolution in this area. A total of 31 water samples were collected in this study area, including 11 rivers and 20 groundwater samples, and analyzed for temperature, pH, Eh, electrical conductivity, total dissolved solids, major ions and 18 trace elements concentrations. The most waters were grouped into Ca–Mg–HCO3 type. Reaction of silicate minerals is a key responsible for geochemical processes in the study area. Trace elements concentrations are low and Surface waters have lower trace element abundances compared to groundwater. Arsenic compared with other trace elements; shows a rather wide concentration range in the sampled waters, ranging between 0.6 to 502 µg/l and is not correlated with pH and Eh in surface water but are a function of pH and Eh in groundwater.