The hydrogen storage performance of ball-milled sample of cast Mg-6 wt% Ni alloy was investigated. Morphology and microstructure of the cast sample and achieved powders were evaluated by high-resolution scanning electron microscopy. The activation characteristics of ball-milled alloy are compared with those of the materials obtained by ball-milling of 5 wt% multi-walled carbon nanotubes (MWCNTs) for 2 hours. MWCNTs enhanced the absorption kinetics considerably. The hydrogen content of modified powder by MWCNTs reached to the maximum hydrogen capacity within two minutes of exposure to hydrogen at 370°C and 2MPa pressure. The evidence is provided that nucleation and growth of hydrides accelerate drastically by homogenously distribution of MWCNTs on the surface of ball-milled powders.