This paper addresses the feasibility of T-joint welding using the friction stir welding (FWS) process. The aims are (i) to study the dissimilar welding of T configuration by optimal tool and process parameter on weld quality, (ii) to understand the joint strength, i.e. tensile, hardness, and morphological analysis. To ensure the objective, a 3 mm aluminium plate of AA6061 alloy was used as a skin and 2 mm AA5052 alloy as a stringer for T-joint. T-joint was performed with a special fixture to hold the T-shaped structure without any misalignment and a cylindrical taper tool was developed with High-carbon high-chromium (HCHCR) steel. After the welding, a tensile test was conducted and the result indicated that 1.22 times higher yield strength was obtained in the proposed T-joint. Similarly, the maximum hardness obtained was 66.18 Hv at FZ, and 64.25 Hv and 43 Hv in the HAZ region, respectively, skin and stringer. Microstructural analysis provided insights into the weld morphology and its influence on mechanical properties. The results demonstrate that friction stir welding is a viable technique for producing high-quality T-joints in dissimilar aluminium alloys, with significant enhancements in mechanical properties achieved through optimized parameters and tooling.