The hydrogen desorption properties of Mg-rich alloys are significantly improved by nanostructure formation. This effect is examined for a melt-spun and nanocrystallized Mg–Ni–La alloy by pressure–composition isotherm (PCT) and thermal desorption spectrum (TDS) measurements. This alloy exhibits fast desorption kinetics and favorable PCT characteristics with an H-capacity of ∼4.6wt%. TDS measurements reveal a definite peak ascribable to release of hydrogen from nanoboundaries, in addition to those associated with decompositions of hydrides such as MgH 2 , Mg 2 NiH 4 and LaH 3 . Hydrogen transport along the nanoboundaries appears to facilitate the desorption kinetics in this alloy.