Friction stir welding is a rising solid-state material joining procedure which has revolutionized the world. It’s majorly utilized for joining aluminum and alike soft materials for industrial and commercial use. The present study comprised of experimental investigation of FSW operation parameters like tool rotational speed, tool transversal speed, and tool pin geometry profile on the tensile strength of friction stir welded joint between Al alloy 6061-T651 and Al alloy 5083-H321. Two newly developed pin profiles that are cylindrical quad slotted and cylindrical threaded quad slotted are used along with cyclindrical threaded tool pin profiles. Tool rotation speed selected for the operation are 600, 900 and 1200 revolution per minute and tool transversal speeds are 20, 40 and 60 milimetre per minute. Tools were produced from TS (Tool Steel) H-13. The FSW operation was conducted on vertical-axis milling machine. Tensile test, most widely used to experimentally varrify the strength of material is applied to check the weld strength performed through FSW. Taguchi design of experiment was used in order to investigate the optimum parameters with minimum number of experiments. Analysis of variance (ANOVA) and regression analysis are applied for evaluating the relative significance and importance of individual parameters affecting mechanical behavior of the weld joints. The result imply that tool’s pin geometry profile has a significant impact on the strength of weld joint cylindrical threaded quad slotted tool pin profile produced the best weld joints. This study also suggests that the increased motion of plasticized phase of Al in horizontal and vertical trajectory simultaneously, which was achieved with the help of cylindrical treaded quad slotted pin profile gives the best weld joint under the same circumstances in relation to other tools under studies. The study also suggests that best weld was achieved with highest tool rotational speed and lowest tool transversal speed.