In this study, Al/Al2O3/B4C nano-composites were fabricated via the accumulative roll bonding (ARB) process. The grain refinement of the Al/Al2O3/B4C nano-composite strips during the ARB process was studied. Microstructural characterizations of the fabricated composites after 2, 5, and 9 cycles were performed by transmission electron microscopy (TEM). The results showed that the composite sample, after 9 cycles, was filled with homogenously distributed ultra fine grains with an average grain size of 230 nm. The findings also revealed that the increase in the dislocation density due to the presence of the nano-sized particles resulted in the grain refinement of the specimens. It was also found that the grain refinement is accelerated by the presence of the refinement particles. © 2013 Elsevier Inc. All rights reserved.