Bimetallic catalysts offer unique advantages for improving the hydrogen storage performance of MgH2. Herein, Ni3Fe/BC nanocatalysts were prepared via a simple solid phase reduction method using a low-cost biomass charcoal (BC) material as the carrier. The onset temperature of hydrogen release for the MgH2 + 10 wt% Ni3Fe/BC composite was 184.5 °C, which is 155.5 °C lower than that of pure MgH2. The dehydrogenated composite starts to absorb hydrogen at as low as 30 °C and is able to absorb 5.35 wt% of H2 within 10 min under 3 MPa hydrogen pressure at 150 °C. In comparison to pure MgH2, the apparent activation energies of dehydrogenation and rehydrogenation of MgH2 + 10 wt% Ni3Fe/BC were reduced by 52.89 kJ mol−1 and 23.28 kJ mol−1, respectively. The hydrogen storage capacity of the composite was maintained in 20 de/rehydrogenation cycles, indicating a good cycling stability. X-Ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray energy dispersive spectroscopy (EDS) characterization reveal that the in situ formation of multiphases Mg2Ni and Fe catalysts during the hydrogen uptake and release reaction and the transformation of Mg2Ni/Mg2NiH4 together contribute to the superior hydrogen adsorption and desorption performance of MgH2.