In this report, Cu nano particles have been prepared by direct electrochemical reduction from CuO nano particles and the reduction mechanism was investigated. To investigate the reduction mechanism, CuO has been deposited on the AISI 430 by magnetron sputtering in various Ar/O-2 ratio and the cyclic voltammetry (CV) was performed in 0.5 M NaCl solution at 300 K. This result indicated that the oxygen from the CuO was ionized at -0.874 V (versus SCE) and reduced to Cu. To fabricate Cu nano particles, we employed CuO nano particles, which were prepared by a conventional mechanical milling, with a dc rectifier and the specific electrochemical cell. The structure of the films and nano particles were analyzed by XRD, SEM/EDS and XPS. (c) 2005 Elsevier B.V. All rights reserved.