The mechanical alloying (MA) of the 2Mg-0.5Ni-0.5Ge mixture at room temperature under argon atmosphere was investigated. The crystal structure, morphology and thermal stability of the products were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis and differential scanning calorimetry. A new alloy in the Mg-Ni-Ge system was synthesized by MA of the 2Mg-0.5Ni-0.5Ge mixture and by the combination of MA and subsequent thermal treatment. No evidence of the formation of Ni-Ge compounds was observed. The new ternary alloy can be considered isostructural with Mg 3 Ni 2 M-type compound, with a F cubic cell and a lattice parameter a=11.521 Å. Thermal studies show that the Mg-Ge-Ni alloy is stable upon heating up to 500 o C.