We describe a simplified synthesis method for the metal hydride Mg2NiH4, based on the direct reaction of MgH2 hydride and Ni metal (2MgH(2) + Ni -> Mg2NiH4) by ball-milling under nitrogen atmosphere at room temperature. Different milling times and different MgH2:Ni atomic stoichiometries have been evaluated, in order to optimize the synthesis conditions. X-ray diffraction (XRD) analysis was used to identify the purity of the samples and quantify the present phases, through Rietveld analyses of the crystal structure, which can be defined in the cubic space group Fm (3) over barm. Thermogravimetric analysis has been carried out to determine not only the hydrogen desorption temperature but also the hydrogen contents. Scanning electron microscopy images show an average particle size of 1-2 mu m for Mg2NiH4; the microstructure presents a sponge-like aspect adequate to favor the absorption and desorption processes. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.