This document presents an experimental investigation of the tensile strength and deflection characteristics of friction stir welded aluminum AA 6351 alloy joints. Tensile and deflection tests were carried out on friction stir welded specimens made with different tool rotational speeds. The results showed that tensile strength and breaking load increased with increasing rotational speed up to 950 rpm, but decreased at higher speeds. Deflections of friction stir welded specimens under different loads were similar to those of the base material specimens, indicating that friction stir welding does not negatively impact the deflection properties of the aluminum alloy. Overall, the joints welded at 950 rpm exhibited the highest tensile strength and breaking load compared to other welding conditions tested.