Mg3GeNi2 hydrogen storage electrode alloy was synthesized successfully via mechanical milling followed by sintering, and its electrochemical performance as the negative electrode material in a nickel-metal hydride (Ni-MH) battery was studied for the first time. Then, different amounts of nano-nickel were added to the selected alloy with the pre-milling duration of 60 h to further improve the electrochemical performance. XRD results indicate that partial substitution of Mg by Ge in Mg2Ni can form a stable new phase of Mg3GeNi2 with excellent cycle stability. Nano-Ni addition can increase dramatically the discharge capacity and electrochemical kinetics of the alloy, which is attributed to the good electrocatalytic capability of the nano-Ni. The Mg3GeNi2-5 wt.% nano-Ni sample shows the optimum overall properties with the best electrochemical kinetics and the highest discharge capacity. •Mg3GeNi2 alloy was synthesized successfully via mechanical milling and sintering.•Electrochemical hydrogen storage of Mg3GeNi2 alloy was studied for the first time.•Mg3GeNi2 alloy exhibits excellent charge and discharge cycling stability.•Nano-nickel addition increases dramatically the discharge capacity and kinetics.