The effect of single and double substitution with lightweight elements Boron (B) and Lithium (Li) on the thermodynamic properties of MgH2 are investigated by using first principles calculations. Our results show an improvement of hydrogen storage properties of double substituted MgH2, in contrast to the case of single substitution, along with a remarkable increase of its gravimetric and volumetric capacities which exceed those of pure MgH2. Given that Mg4LiBH12 exposes a heat of formation around -32.03 kj/mol as well as a gravimetric and volumetric capacity of 9.45 wt% and 123.08 gH(2)/l respectively, it may be considered as a potential candidate for hydrogen storage transportation applications. A detailed analysis of the density of states and charge transfer, of the studied systems, is presented to understand the underlying mechanisms behind MgH2 thermodynamics improvements. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.