The unfavorable de/re-hydrogenation aspects of high storage capacity material, Mg can be overcome by synthesis of composites with known intermetallic hydrogen storage alloys. In this work, a new additive, ZrFe2Hx intermetallic hydride, is used to synthesize MgH2-ZrFe2Hx nanocomposite by reactive mechanical milling technique. Also this report describes the comparison of hydrogen sorption behavior of MgH2-ZrFe2 and MgH2-ZrFe2Hx nanocomposites. It is found that the composite containing ZrFe2 and ZrFe2Hx leads to decrease in desorption temperature from 410 degrees C (for MgH2) to 350 and 290 degrees C respectively. The activation energy for rehydrogenation of composite is found to be similar to 61 kJ/mol. This is lowered by 30 kJ/mol compared to the pristine milled MgH2 (92 kJ/mol). Thus, the results show significant improvement of hydrogenation behavior with the addition of ZrFe2Hx Reasons for better catalytic activity achieved by using ZrFe2Hx have been put forwarded. Based on the present studies it can be suggest that the use of hydride version instead of the parent intermetallic phase for synthesizing the composite with MgH2 has a distinct advantage in improving the hydrogenation behavior of MgH2. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.