In the present paper, Mg3MnNi2Hx hydride has been synthesized using the reactive mechanical alloying (RMA) process, i.e. employing a simple one-stage technology instead of the complicated four-stage route used in [1] for synthesis of the same hydride (the milling powder of pure Mg, Ni and Mn metals and of Mg2Ni alloy in argon atmosphere followed by their pressing, sintering and hydriding from the gaseous phase). The Mg3MnNi2Hx hydride derived by the RMA method was studied by thermodesorption spectroscopy. Similarly to Mg3MnNi2Hx hydride derived in [1], the hydride obtained in the present paper reveals decreased thermal stability and close hydrogenation capacity (1.35 wt%).