Oxidation of methanol was studied in alkaline solution on bimetallic Ir/Pt(poly) catalysts prepared by the spontaneous deposition of Ir on polycrystalline Pt. Nano-scale surface properties of Ir/Pt(poly) catalysts were revealed by ex situ Atomic Force Microscopy imaging. Modified electrodes were characterized in situ electrochemically by cyclic voltammetry in 0.1 M KOH. Investigations of the methanol oxidation in the same alkaline solution showed that Ir/Pt(poly) electrode obtained after 1 minute Ir deposition, which is equivalent to 80% Ir coverage, showed improved activity with respect to both constitutive metals. The observed synergism on the methanol oxidation activity was ascribed to both bifunctional and electronic effects that are induced by the presence of spontaneously deposited Ir. The origin of the synergism and the possible methanol oxidation pathways were discussed on the basis of the activities of the Ir/Pt(poly) electrodes for the oxidation of the most probable reaction intermediates, CO and formaldehyde, in the same alkaline solution.