The direct and solvent-free synthesis of yttrium borohydride was achieved by reactive ball milling of yttrium hydride in diborane/hydrogen atmosphere. The product contains only the solid elemental hydride as remaining contaminant. Yields above 75% were obtained. The product crystallizes in the cubic α phase and releases hydrogen above 460 K. The decomposition was measured by in situ X-ray diffraction and the hydrogen release was monitored gravimetrically in conjunction with infrared gas analysis. No diborane was detected during the decomposition. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.