Keggin-type heteropolyanion H3PMo12O40 encapsulated by a cationic surfactant dioctadecyldimethylammonium chloride (DODA-Cl) has been assembled on ITO substrates using an electrophoretic approach. The films were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), IR spectra, X-ray photoelectron spectra (XPS) and cyclic voltammetry. The AFM images exhibit a spherical assembly of surfactant-encapsulated complex (SEC) nanoparticles with uniform size. The SEM was also used to investigate the surface topography. It is the first report that the thin films of SEC are fabricated using this method, which provides a new route to explore the possibility of application to polyoxometalate-based hybrid inorganic-organic materials. (C) 2009 Elsevier Inc. All rights reserved.