(Mg1−x Zr x )2Ni (x=0.0, 0.1, 0.2, 0.3 and 0.4) hydrogen-storage alloy electrodes are synthesized by means of a mechanical alloying process using a planetary ball mill. After milling for 160 h, (Mg1−x Zr x )2Ni alloy with x=0.0 remained the nanocrystalline phase. By contrast, Zr addition to this alloy enhances the structural disorder and amorphization. The discharge capacity of a (Mg1−x Zr x )2Ni electrode increases with Zr content and reaches the highest capacity of 530 mAh g−1 at x=0.3, then decreases to 230 mAh g−1 at x=0.4, i.e., lower than that of pure Mg2Ni. Cyclic stability and rate capability vary with Zr addition.