Copper particles were electrolessly deposited on a palladium aerosol activated polymer membrane in the presence of ultrasound. An application of ultrasound introduced a faster deposition (220μgmin −1 in deposition rate) and finer copper particles (9nm in crystallite size) than those (11 and 41μgmin −1 ; 27 and 32nm) in the absence of ultrasound (i.e. respectively 20 and 45°C in bath temperature with mechanical agitation). A better performance of methanol steam reforming (0.59 in mean conversion during 5h operation; 1.3 and 1.6 times respectively higher than those from 20 to 45°C cases) at a 300°C reaction temperature was materialized for the ultrasound application, probably due to a finer (i.e. a more textured) copper particle deposition on a polymer membrane.