Zn(BH4)2 made in our former investigation and Ni were mixed with MgH2 to promote the hydrogen absorption and release features of Mg. A 96 w/o MgH2 + 2 w/o Ni + 2 w/o Zn(BH4)2 sample [named MgH2–4NZ] was prepared by milling in a planetary ball mill in a hydrogen atmosphere. The proportion of the additive was small (4 w/o) in order to increase hydrogen absorbing and releasing rates without majorly sacrificing the hydrogen-storage capacity. The hydrogen absorption and release features of the MgH2–4NZ were inspected in detail and compared with those of 99 w/o MgH2 + 1 w/o Zn(BH4)2 [named MgH2–1Z] and 95 w/o MgH2 + 2.5 w/o Ni + 2.5 w/o Zn(BH4)2 [named MgH2–5NZ] samples. The activation of the MgH2–4NZ was not required. The MgH2–4NZ had a useful hydrogen-storage capacity (the quantity of hydrogen absorbed after 60 min) of about 5.5 w/o at the first cycle. At the first cycle, the MgH2–4NZ absorbed 3.84 w/o hydrogen after 5 min and 5.47 w/o hydrogen after 60 min at 593 K in 12 bar hydrogen. The MgH2–4NZ had a higher releasing rate, larger amounts of hydrogen absorbed and released after 60 min, and a better cycling capability than the MgH2–1Z. Staying of Ni (as Mg2Ni) and a larger amount of Zn among particles is believed to have led to the better cycling capability of the MgH2–4NZ.