Aluminum oxide (Al2O3) nanoparticles are capable of improving the material characteristics if reinforced to soft and low strength material. The major limitation in the utilization of Al alloy 6061 in medium to heavy stress applications such as automobile, defense, transportations, and aerospace is low hardness and strength. In order to overcome the deficiency of Al6061, nano-Al2O3 reinforced Al6061 matrix nanocomposite (AMNC) was successfully fabricated on machinated aluminum stir casting furnace. Al2O3 nanoparticles in 2,4,6 and 8 wt.% were reinforced in the Al6061 matrix and the effect on mechanical and microstructure behavior was investigated by field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), hardness, and tensile testing methods. Higher magnification FESEM micrographs revealed that reinforcement of nano-Al2O3 leads to considerable grain refinement and uniform distribution with less porosity. The mechanical properties results showed enhancement in tensile strength (by 130%), hardness (by 156%), yield stress (by 360%) with reinforcement of nano-Al2O3 over the base alloy Al6061. It was observed that the nano size of Al2O3 particles, the quantity of reinforcement, and the stir casting process were effective factors on the microstructure and mechanical properties enhancement. © 2022 IOP Publishing Ltd.