The effect of joining parameters and tool pin profile on microstructure and mechanical properties of semi-solid metal A356 joints produced by friction stir welding was investigated. In this work, the joints were made by using a fixed rotating speed of 1,750 rpm with varying welding speed of 80, 120 and 160 mm/min and 30 of tool angle. In addition, two different types of tool pins, cylindrical and square pin, were applied. The optical micrograph shows no voids, cracks or other weld defects. The Scanning electron microscope (SEM) reveals fine microstructure and uniform dispersion of Si (Silicon) particles obtained from cylindrical pin than that of square pin. The Variation of hardness throughout the weld also reveals slightly greater at the stir zone for every welding speed for both pins. Transverse and longitudinal tensile strengths obtained from cylindrical pin are greater than square pin. Furthermore, the joint made from 1,750 rpm, 160 mm/min with cylindrical pin shows highest strength.