The friction stir welding is a solid state welding in which welding takes place at a temperature below the melting point. This welding is also known as green technology welding as no harmful gases are generated, as well as fluxes are not formed. In this process joining of two dissimilar materials can be achieved. Through this welding one can overcome defects like porosity, solidification, cracks etc by selecting suitable wilding parameters. Present work investigates the effect of different tool pin geometries on mechanical properties of friction stir welded AA6061 and AA7075 alloys keeping the process parameters constant. The welding is carried with process parameters 1000rpm, 50mm/min and 5KN as tool rotational speed, welding speed and axial load respectively, and for four different pin geometries: (a) cylindrical pin, (B) triangular pin, (c) square pin and (d) hexagonal pin. The welded samples are characterized by mechanical properties like tensile strength and micro Vickers hardness test. By considering the both properties the hexagonal pin shown better characteristics under optimum process parameters.