The implementation of magnesium (Mg) as a hydrogen-storage medium has long been restricted because of its rather sluggish hydrogen sorption at high temperatures. Here, we report a method for using hydrogen-induced Mg–Zr interfacial coupling to manipulate the migration of hydrogen atoms and thus tune their uptake and release in a micrometer-sized Mg-rich composite. The associated Mg–Zr–H interfaces were assembled in situ by high-pressure ball milling and isothermal treatment of MgH₂ and Zr powders under a hydrogen atmosphere. The interfaces gradually disintegrated upon MgH₂ desorption but also recovered their original compositions upon absorption while the ZrH₂ originating from Zr hydrogenation remained completely unchanged. Compared to pure MgH₂, the hydrogen sorption of the Mg–Zr–H composite was thus shown to be dramatically faster at lower temperatures, whereby it not only absorbed hydrogen close to saturation at 100 °C within 2 h, while the pure Mg did not absorb hydrogen at all, but also started to release hydrogen at ∼235 °C with a reduction in the activation energy of desorption by ∼40 kJ mol⁻¹. These remarkable enhancements cannot be explained by the decrease in the size of the MgH₂ grains alone but are most likely due to the introduction of Mg–Zr–H interfaces and large fractions of defects that provide channels for facile hydrogen dissociation and migration into the Mg/MgH₂ matrix.