A simple approach for the synthesis of nanosized platinum particles supported on ordered mesoporous carbons (OMCs) was described. For the first time, we successfully used the positively charged poly-(diallydimethylammonium chloride, PDDA) to wrap OMCs and attached Pt nanoparticies (OMCs-PDDA/Pt) via electrostatic interaction. The obtained OMCs-PDDA/Pt nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and electrochemical methods. TEM images reveal that the Pt nanoparticles with an average size of similar to 2.88 nm are uniformly dispersed on the surface of OMCs-PDDA. The electrocatalytic behavior of OMCs-PDDA/Pt modified glassy carbon (GC) electrode was investigated by cyclic voltammetry, current-time and chronoamperometry methods using hydrazine as a redox probe. The electrochemical results indicate that the OMCs-PDDA/Pt exhibit a good electrocatalytic activity toward the oxidation of hydrazine than that of OMCs/Pt. All these electrochemical measurements confirm the fact that the OMCs-PDDA/Pt nanocomposites may have applications in biological and environmental sensors. (C) 2011 Elsevier Ltd. All rights reserved.