One of the recent novel joining mechanisms in the solid-state-welding process is Friction Stir Welding (FSW). The process is extensively used in joining similar and dissimilar materials as well. This research studied and found the optimum process parameters of FSW based on the temperature simulation results on a 5 mm 6061 Al alloy sheet with a butt joint configuration. Steady-state heat transfer analysis was performed using a transient thermal workbench to predict and identify the optimum parameters grounded on the simulation welding temperature result. The parameters are optimized using the hybrid Taguchi L9 orthogonal array and Grey relation analysis method with a larger is better quality characteristic. Mechanical properties of the weld joints' such as hardness and tensile strength, were studied at an ambient temperature. The result revealed that a higher rotational speed with a minimum traverse speed and taper threaded tool pin impart the optimum parameter settings. Analysis of variance (ANOVA) was carried out also to determine the effects of each process parameter. At a 95 % confidence interval, rotational and traverse speeds show significant characteristics. The joint efficiency reached 92.25% of the base metal at a maximum welding temperature. Additionally, the microstructure of the stir weld zone of the specimen was studied as well. Metallographic Characterization carried out using Scanning Electron Microscope (SEM) revealed the microstructure of the samples after the weld did not show any significant change with the base metal. Furthermore, this study scheme can be extended to thick non-ferrous, ferrous, and metal-based composite materials, too.