In this current research work, the effect of tool rotational speed on micro structural and mechanical properties of Friction stir welded 5083 Aluminium alloy was studied. The welding parameters, especially tool rotational speed plays a major role in deciding the weld quality. It is observed that higher mechanical properties are obtained at a rotation speed of 710 rpm. It is also observed that the fine microstructure obtained at the above mentioned condition. The mechanical properties were observed & correlated with the microstructureand fracture features.