This paper investigates a facile and one-step synthesis of trimetallic magnetic Cu@FeNi core-shell nanoparticles, which are composed of crystalline Cu cores and amorphous FeNi shells, at room temperature under ambient atmosphere within 2 min. It is found that among the Cu@FeNi system, [email protected] shows the best synergistic performance for catalyzing the hydrolytic dehydrogenation of ammonia borane with the activation energy of 32.9 kJ/mol, being lower than most of the reported data, and the catalytic activity of [email protected] is much better than its monometallic, bimetallic and trimetallic counterparts whether in states of pure metals, alloys or physical mixtures. Further, the present catalyst has a good recycle stability with an easy magnetic separation method. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.