Abstract: Friction stir welding was performed on 2 mm thick 6061 aluminum alloy sheets to investigate the effects of process parameters, including tool rotational speed and traverse speed, on the mechanical properties of the welded joint. The results show that sound joints with favorable mechanical properties can be obtained within a reasonable parameter range, with tool rotational speed of 1000 r/min-1600 r/min and traverse speed of 100 mm/min-500 mm/min. When the tool rotational speed is 1200 r/min and the traverse speed is 300 mm/min, the tensile strength of the welded joint reaches the maximum value of 229 MPa, corresponding to 76% of that of the base metal. The tensile fracture occurres in the heat-affected zone on the retreating side, exhibiting a mixed fracture mode with both ductile and brittle features. The microhardness distribution across the joint presented a typical “W” shape, with the lowest hardness of approximately 55 HV observed in the heat-affected zone. The hardness in the nugget zone increases significantly but remains lower than that of the base metal. In addition, the impact toughness of the welded joint is higher than that of the base metal. The results provide a reference for the optimization of friction stir welding process parameters for 6061 aluminum alloy.