Copper oxide nanoparticles were synthesized by thermal decomposition of the copper (II) nitrate (Cu(NO(3))(2)center dot 3H(2)O) based aerosol droplets at different temperatures. The effects of reaction temperature on size, morphology and crystallinity of copper oxide nanoparticles under air atmosphere were studied. Scanning Electron Microscopy (SEM) analyses revealed that nearly 30 inn sized copper oxide spherical nanoparticles were prepared. X-ray diffraction (XRD) patterns indicate that obtained nanoparticles have tenorite structure with monoclinic lattice. Also, Energy Dispersive Spectrometry (EDS) analyses show that the weight ratios of Cu to O are for the copper oxide nanoparticles are the same ratio with tenorite.