It is believed that the dehydrogenation of LiNH2BH3 (LAB) proceeds through a combination of the decomposition of the LiBH2NH3 (LBA) and LAB isomers. The dehydrogenation of LBA, an isomer of LAB, is discussed in this article. It is demonstrated that the loss of H2 from LBA takes place in a two-step reaction. Studies of the dehydrogenation process were performed using Møller–Plesset second-order perturbation theory with a 6-311++G(3df,2pd) basis set. The intrinsic reaction coordinate was calculated to determine the minimum energy paths. Finally, the rate constants were obtained using the transition-state theory (TST), TST/Eckart, canonical variational transition-state theory (CVT), CVT/small-curvature tunneling correction, and CVT/zero-curvature tunneling correction methods from 200 to 2500 K. This is the first report on a different dehydrogenation mechanism for an alkali-metal amidoborane, and the energy barrier of LBA is much lower than that of the traditionally studied LAB. © 2012 Wiley Periodicals, Inc.