The present work demonstrates the reversible hydrogen storage properties of the ternary alloy Mg18In1Ni3, which is prepared by ball-milling Mg(In) solid solution with Ni powder. The two-step dehydriding mechanism of hydrogenated Mg18In1Ni3 is revealed, namely the decomposition of MgH2 is involved with different intermetallic compounds or Ni, which leads to the formation of Mg2Ni(In) solid solution or unknown ternary Mg- In-Ni alloy phase. As a result, the alloy Mg18In1Ni3 shows improved thermodynamics in comparison with pure Mg. The Ni addition also results in the kinetic improvement, and the minimum desorption temperature is reduced down to 503 K, which is a great decrease comparing with that for Mg-In binary alloy. The composition and microstructure of Mg-In-Ni ternary alloy could be further optimized for better hydrogen storage properties. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.