The present study features analytical and experimental results of AA2198-T8 joints produced by the refill friction stir spot welding of 1.6-mm-thick sheets. The selection of proper parameters for this process, such as tool rotational speed (RS), welding time (WT), and tool plunge depth (PD), played an important role in assuring weld strength. In this work, experimental tests were carried out based on the welding conditions according to Taguchi method, in order to determine optimal welding parameters and investigate the effect of those in the joint’s mechanical properties and welded area. Results based on lap shear strength showed that RS and PD were responsible for more than 80% of strength variance, while the analysis based on the stir zone area measurement of the welds endorsed that WT had an insignificant contribution to the strength. Higher strength was correlated to bigger stir zone area, which results from higher RS and PD values.