P-type copper oxide nanowires (NWs) were grown on metallic copper plates and sapphire substrates. Significant variations in the morphology and distribution of the NWs, due to underlying differences in the growth mechanism and the NW densities, were observed based on the nature of the substrate utilized. The use of copper plates induced an extremely high density of copper oxide nanowires on temperature-dependent copper oxide layers. However, the sapphire substrates gave rise to highly superior CuO NWs without any involvement of an oxide layer, leading to a low density of copper oxide NWs. Systematic characterization of the as-grown copper oxide NWs using X-ray photoelectron microscopy and Raman spectroscopy indicated that the NWs were comprised of CuO with Cu2+ metallic ions.