Mechanical alloying was employed to produce the nanocomposite Al2O3-Ni. It was found that the mechanical alloying of a mixture of NiO and α-Al2O3 generated a highly disordered structure. Reduction under a hydrogen atmosphere led to formation of nano-sized Ni crystallites in the Al2O3 matrix. Relatively high BET specific surface areas indicate that the sub-micron nanocomposite particles have a porous structure. In comparison with the co-precipitated powder, the mechanical alloying-derived powder shows smaller particle/agglomerate size and much higher Ni reducibility. Multi-walled carbon nanotubes with a high production yield were successfully synthesized by using the mechanical alloying-derived nanocomposite as the catalyst.