Electrochemical polymerization of aniline on nanostructured Ni substrates was investigated. To this aim, the Ni substrate electrodes were prepared by casting various samples of Ni nanoparticles having different morphologies. The electropolymerization on these different nanostructured Ni substrates was systematically investigated by means of comparative results obtained from cyclic voltammetry and electron microscopy as representatives of electrochemical behavior and morphology, respectively. Since the Ni nanoparticles are the beginning sites for the polymer growth, polyaniline morphology is strongly controlled by the nature of the Ni nanoparticles associated with chemical properties rather than geometrical shape. In conclusions, although the substrate surfaces had a similar nanostructure, but due to the difference in their chemical properties, the morphologies electrochemical behaviors of the polyaniline films electrodeposited on these substrates are significantly different. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 1579-1586, 2011