The mechanical properties of the friction stir welds of the oxygen free copper (OFC) and 60%Cu-40%Zn copper alloy(60/40 brass) were investigated. The defect-free welds were obtained in a relatively wide range of welding conditions; the tool rotation speed had rpm of 1000 to 2000 in the OFC and 1000 to 1500 in the 60/40 brass, with the welding speed of 500 to 2000 mm/min. The SZ hardness values of the OFC welds were almost the same or slightly lower than those of the base metal. However, the SZ hardness values of the 60/40 brass in all welding conditions were much higher than those of the base metal. The SZ hardness values of both metals increase with a decrease in heat input. The tensile properties of the all-SZ showed relative correspondence to the variation of the SZ hardness values.