This study was carried out to better understand the chemical composition, microstructure, and hydrogen properties of Mg binary alloys. In this study, Mg60-Ni40 and Mg80-Ni20 (wt.%) alloy ribbons with different microstructures have been produced by the melt spinning method. The structural, hydriding, and dehydriding properties of the alloys were evaluated. The phase constitutions and microstructures were characterized by XRD and SEM studies. Microstructural grain sizes measured for Mg60-Ni40 alloy ribbons were in the range of 1-5 mu m, and the alloy contained finely dispersed Mg and Mg2Ni phases. In the case of Mg80-Ni20 alloy ribbons, the microstructural grain sizes were measured as less than 1 mu m. The hydrogen absorption and desorption capacities and kinetics of these two alloys were found to be highly dependent on microstructure and phase properties. Also, the amount of Ni content affected both the hydrogen storage capacities and kinetics for both of the Mg-Ni binary alloys. The increasing amount of Ni resulted in reduced hydrogen absorption capacity. The Mg60-Ni40 and Mg80-Ni20 alloy ribbons demonstrated superior hydrogenation absorption capacity at 350 degrees C and reversibly absorbed about 4.62 and 5.51 (wt.%) mass hydrogen, respectively.