The effect of friction stir welding (FSW) T-joints for 3 mm AA6061-T6 aluminum alloy plates on mechanical properties has been investigated in the current work by using the nine different tool shapes that were designed according to Taguchi orthogonal array (OA) without changing the process parameters (tool rotation speed, welding speed, tool tilt angle, plunge depth, and die radii). Four variable geometrical parameters (shoulder diameter (mm), pin diameter (mm), pin angle (α, deg), and groove pin shape) with three levels for each parameter have been used. The signal to noise (S/N) ratio technique was performed for analyzing results (ultimate tensile strength across the skins (UTSSkins) and ultimate tensile strength across the stringers (UTSStringers)) using the statistical software (minitabtm® 16) to establish the best optimum condition. The conformation test was also performed by fulfilling the welding process at the optimum condition to compare the theoretical and experimental results. In addition, the analysis of variance (ANOVA) technique was performed using the statistical software (design of experiments, doe pro xl) to identify the significant factors affecting on the (UTSSkins and UTSStringers).