Friction stir welding (FSW) is a solid-state joining process that leads to several advantages over fusion welding methods as problems associated with cooling from the liquid phase are avoided. In the current research, a new method is presented to improve the microstructure and mechanical properties of joint obtained using FSW. In this method, the joining workpieces are vibrated during FSW. The joining workpieces are fixed on fixture in a butt position and the fixture is vibrated mechanically normal to weld line through camshaft mechanism. The new method is described as friction stir vibration welding (FSVW) process. Microstructure and mechanical properties of welded specimens using FSW and FSVW processes are compared. The results show that weld region grain size of FSV welded specimen is lower than that in specimen welded by FSW for about 30% and the ultimate tensile strength of joint obtained using the former process is higher than that relating to the latter one for about 12%. This is attributed to more generation of dislocations and correspondingly enhanced dynamic recrystallization as vibration is applied. The results also indicate that the weld region grain size of FSV welded specimen increases and mechanical properties of joint decrease as tool rotation speed increases and traverse speed decreases. This is related to temperature increase during FSVW. It is concluded that FSVW is a proper candidate for FSW and its application is recommended for industries.