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This work presents the microstructural evolution of mechanically alloyed Mg2Ni0.5Co0.5 and a study of its hydriding properties. Mg, Ni and Co elemental powders (atomic ratios of 2:0.5:0.5, respectively) were mechanically alloyed in a Spex 8000D high-energy mill for 36 h (amorphous sample) and subsequently submitted to a thermal treatment at 673 K for 15 min (nanocrystalline sample). The characterizations of the samples were performed with X-ray diffraction. A Sievert-type volumetric hydriding process was done at 363 K and with hydrogen pressure of 2 MPa. Desorption process was evaluated through differential scanning calorimetry. Based on the obtained results, it is possible to conclude that the amorphous structure absorbs more hydrogen, reaching a maximum of 3.6 wt. % H. Desorption process events depend on amorphous or nanocrystalline states. [ABSTRACT FROM AUTHOR]