Co-Co(2)B and Ni-Ni(3)B nanocomposites were synthesized by the reduction of Co(2+) and Ni(2+) ions using ammonia-borane in methanol. The Co-Ni-B nanocomposite was synthesized by the co-reduction of Co(2+) and Ni(2+) ions. The catalytic activities of these metal nanocomposites were studied for the dehydrogenation of ammonia-borane in methanol. Three moles of H(2) were liberated in 2.5 min and 4.2 min in case of Co-Co(2)B and Ni-Ni(3)B nanocomposites, respectively (catalyst/AB = 0.2). The Co-Ni-B nanocomposite showed greater activity compared to individual metal-metal boride nanocomposites: 3 moles of H(2) were liberated in 1.5 min (catalyst/AB = 0.2). The catalysts were highly recyclable and the activities remained almost unchanged even after several cycles.