Nominal Mg3LaNi0.1 alloy was prepared by a single roller melt-spun method. The phase structure and hydrogen storage properties of the obtained ribbons were studied by X-Ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) analysis and pressure-composition isotherm (PCI) measurements. The melt-spun Mg3LaNi0.1 alloy was composed of Mg3La phase, while fine LaMg2Ni grains were precipitated after an aging treatment at room temperature. Both Mg3La and LaMg2Ni undertook disproportion reactions upon hydrogenation and decomposed into MgH2, LaH3 and Mg2NiH4. The melt-spun alloy shows excellent hydrogen absorption kinetics and lowered desorption temperature comparing with the induction-melted alloy, and a maximum hydrogen storage capacity of 3.1 wt.% and a minimum hydrogen desorption temperature of 224 degrees C were achieved. This improvement on the hydrogen storage properties was attributed to the catalytic role of in-situ formed nanocrystalline Mg2Ni and LaH2. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.