Particulate reinforced aluminum matrix composites have recently become a major focus of attention in aerospace, motor sport and automotive industrial fields due to their several attractive advantages over conventional base alloys, such as high specific stiffness and strength to weight ratio at room or elevated temperatures. Friction stir welding is a promising candidate for joining particulate reinforced aluminum matrix composites since this method is a solid state process, therefore, the formation of brittle solidification products are not easily produced; the energy input and distortion are significantly lower than in fusion welding techniques, thus improving the welding properties. In this research, Al- 5Vol%Al 2 O 3 composite was produced after 10 cycles of accumulative roll bonding process. Then, the composites were friction stir welded using 9 different welding parameters including rotation speeds of 900, 1120 and 1400rpm and welding speeds of 63, 80 and 100mm/min. A K type thermocouple was used to record the temperature of the weld line. This thermocouple was fixed in retreating side of the weld line. On the other hand, in order to study the effects of welding tool, at a specific welding parameter, effects of four different pin profiles (square, triangular, hexagonal and cylindrical) were evaluated. Microstructural and mechanical assessments were performed using scanning electron microscopy, tensile test and microhardness measurements. The fracture surfaces were examined and the mechanisms of fracture surfaces were also characterized. A uniform distribution was observed after 10 cycles of rolling while no porosity was seen in the matrix/particle interface and adhesion of reinforcement particles to matrix were improved. The mechanical properties of produced composites were better than those of pure annealed aluminum. The initial composite showed ductile fracture with shallow dimples. Some porosity and discontinuity was observed in the samples welded at low rotation speed of the 900rpm and welding speed of 63, 80 and 100mm/min because of inadequate heat input and weak stirring action. Here, the mechanical properties were poor because of discontinuities in microstructure. By increasing the rotation speed, good weld faces were achievied because enough heat input was supplied. The samples welded at rotation speed of 1120rpm-100mm/min, with maximum revolution pitch value (Welding Speed/Rotation Speed) of 0.089mm/r, showed the highest value of tensile strength and hardness and the lowest value of elongation. The samples produced at speed of 1400rpm-63mm/min with minimum revolution pitch value of 0.045mm/r, showed lowest tensile strength and hardness value and the highest value of elongation. Welded samples exhibited ductile fracture and initial shallow dimples become deeper because of heat input of welding process. The results of four different pin profiles showed that the fragmentation and distribution of particles is more desirable while square pin profile was used. The effect of dynamic volume/static volume ratio and pulsating stir of the pin profiles were played the main role in fragmentation and distribution of particles simoltaneously. These two parameters had the highest value in square and triangular pin profiles. In this case, the highest values of tensile strength, hardness and elongation were achieved and it was related to square pin profile. Keywords: Accumulative Roll Bonding, Friction Stir Welding, fragmentation, Revolution pitch, Fractography, pin profiles.