Copper oxide (CuO) nanoparticles (NPs) and copper oxide doped with various percentage of nickel (Ni) (0.5%, 1%, 2%, 5% and 10%) has been successfully prepared using the solid-solid reaction. The obtained powders of these CuO NPs were calcined at varied temperatures of 350°C, 450°C, 550°C and 650°C. These NPs were characterized by Differential thermal analysis (DTA), X-Ray Diffraction (XRD), Field emission scanning electron microscopy (FESEM) and Fourier transformation infrared spectroscopy (FTIR). XRD obtained a pure phase of the as-prepared CuO NPs. The average crystallite size is determined by XRD increases with certain calcinations temperature. Doping of Ni in CuO NPs is extensively studied. The increasing of Ni from 0.5% to 10% decreases the average crystallite size which confirmed by FESEM studies. Moreover, magnetic properties were investigated for CuO, CuO calcined at 650°C and CuO NPs doped with 10% Ni. The magnetic observations illustrated that at the maximum applied the field of 1.5 kOe, the magnetic response with a maximum moment M ≤ 0.01 emu/g for CuO NPs. This could be related to the uncompensated surface spins. Moreover, the magnetic response with a maximum moment is doubled in CuO NPs doped with 10% Ni.