Magnesium hydride (MgH2 ) is a candidate for solid-state hydrogen storage applications. In this work; hydrogen desorption from transition metal doped MgH2 clusters of approximately 1 nm was investigated by density functional theory (PBE functional and Gaussian basis sets). It was found that transition metals were more stable at the surface than in the center of the cluster and that desorption energies of hydrogen atoms bound to such surface doped transition metals were significantly lowered. It was furthermore observed how transition metals attract hydrogens to keep at least four hydrogen atoms coordinated even when the total hydrogen content of the cluster decreases. This effect is associated with migration of the transition metal atoms from the surface sites to the interior sites during the dehydrogenation process; releasing more hydrogen as they diffuse. This diffusion mechanism may account for the fact that a small amount of catalysts is sufficient to improve the kinetics of MgH2 .