Laser ablation has proven to be an effective method for generating nanoparticles. In this work, we have successfully produced pure cupper nanoparticles in fast and one-step method by Nd-YAG irradiation of cupper target with a 1064 and 532 nm laser wavelengths in pure water. The particle size, shape and size distributions were measured using a transmission electron microscope TEM. The UV–VIS spectroscopy has been employed for the optical properties. Nanoparticles with diameters 30 nm were observed to be formed in the colloidal solution. The UV–VIS spectrum of the material shows weak plasmon peak around 620 nm, indicating the formation of copper oxide nanoparticles. A clear blue shift is observed in the direct band gap (4.3 eV) of these nanoparticles presumably to the quantum confinement effects exerted by the nanosize.