Cupric oxide (CuO) nanoparticles have been successfully synthesized via low-temperature thermal decomposition of bis(dimethylglyoximato)copper(II) complex. The synthesized nanoparticles were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS) and Raman spectroscopy. The powder XRD pattern furnished evidence for a monoclinic structure of CuO with average crystallite size 28.9nm. The TEM image showed aggregation of some quasi-spherical nanoparticles. The Raman spectrum showed three characteristic modes of CuO which further affirmed the phasic purity of the obtained material. The CuO nanoparticles studied in an in vitro system using the modified diphenylpicrylhydrazyl (DPPH) method exhibited pronounced antioxidant activity.