Thermal effects of the decomposition of potassium, calcium, and strontium amidoboranes at 354, 421, and 483 K are determined via drop calorimetry. The processes of decomposition are weakly exothermic and accompanied by the evolution of hydrogen. Upon the decomposition of calcium amidoborane at 421 K, a prolonged exothermic process is first observed; it is then followed by an endothermic effect, due possibly to the slow structural rearrangement of the product of decomposition. The solid products of decomposition are characterized by solid-state ¹¹В NMR, FTIR spectroscopy, and mass spectrometry.