Fine Ti5Si3 powder has been mechanochemically synthesized from a mixture of elemental Ti and Si powders. When Ti5Si3 is added as a catalyst into Li3AlH6, it shows a good catalytic ability by reducing the decomposition temperature and improving the decomposition kinetics as well. Although its catalytic effect is not as good as well-known TiCl3, the use of Ti5Si3 has a benefit of releasing more hydrogen than TiCl3 during dehydrogenation. This can be explained by that Ti5Si3, unlike TiCl3, does not incur any chemical reactions with Li3AlH6 and thus remains inert during milling for dispersion.