This article presents the experimental analysis of tool pin-profile effects on the weld zone shape, mechanical properties and microstructure of the friction stir welding (FSW) process. To determine tool pin-profile effects on weld zone shape, mechanical properties and microstructure, four different pin-profile tools were used namely, the cylindrical pin, conical pin, cylindrical-conical pin and stepped-conical pin. The results of the experiment showed that weld-zone shape thickness of the cylindrical-conical tool near the shoulder was the highest and the conical pin-profile tool was the lowest near the bottom of the tool pin with respect to all other tool pin-profiles. Fine grain structure was produced by the stepped-conical pin-profile tool in the weld zone compared with the other three pin-profile tools. Yield strength, ultimate tensile strength, ductility and joint efficiency of the stepped-conical tool were the highest among all the tool pin-profiles. Additionally, this article also explains the effect of weld-zone shape on mechanical properties, showing that the small basin shape of the weld-zone shape produces high yield strength, ultimate tensile strength, ductility and joint efficiency.