A hybrid carbon support is prepared by mixing graphene nanoplates (GNPs) with carbon nanotubes (CNTs) and modifying them with poly dimethyl diallyl ammonium chloride (PDDA). Pd nanoparticles are deposited onto the hybrid support by a microwave-assisted ethylene glycol reduction method. The obtained Pd/GNPs-PDDA-CNTs catalyst exhibits a high catalytic activity toward methanol oxidation in alkaline solution. Scanning electron microscope and transmission electron microscope images show that GNPs and CNTs contact intimately with each other and Pd nanoparticles are uniformly distributed over them. The linear sweeping voltammetry test indicates that Pd/GNPs-PDDA-CNTs has a low onset potential for methanol oxidation, which is attributed to the synergistic interaction between palladium and PDDA, as revealed by the X-ray photoelectron spectroscopy measurement. It is also observed that the poison resistance of the Pd nanocatalyst is improved to some extent due to the modification of the carbon support by the ionic polymer. Graphic abstract