Friction stir welding (FSW) is a solid-state, layer-based metal joining process in which a rotating tool joins metal sheets without complete melting, thereby avoiding issues associated with fusion-based methods, such as porosity and solidification cracks. In this study, the optimization of FSW parameters to improve the tensile strength of joints between Aluminum 1050 (bottom sheet) and 3105 (top sheet) was investigated. Three key parameters tool rotational speed, traverse speed, and tool geometry were selected as influential variables. The experiments were designed according to the Taguchi method (L9), and data analysis was performed using the signal-to-noise (S/N) ratio in the “larger-the-better” mode. The results showed that the optimal combination of parameters maximized the tensile strength of the specimens, and the effect of each parameter on joint quality was determined through main effects analysis. The maximum tensile strength observed was 164.11 MPa, and the experimental mean of the samples was 151.14 ± 7.94 MPa. Analysis indicated that traverse speed had the greatest impact on tensile strength, while rotational speed and tool geometry also played significant roles. This study addresses the optimization of FSW parameters for the dissimilar joint of Al1050 and Al3105, emphasizing that optimal parameters are highly material-dependent. Using the Taguchi method and data analysis, the effects of the parameters and the quality of the joint were thoroughly evaluated, resulting in improved mechanical properties.