The dissociation dynamics of energy-selected neopentylamine cations, (CH 3 ) 3 CCH 2 NH 2 + , were studied using threshold photoelectron photoion coincidence (TPEPICO) spectroscopy in which ion time-of-flight (TOF) distributions are recorded as a function of the ion internal energy. The lowest energy pathway, producing the CH 3 NH 3 + ion, involves a rearrangement of the molecular ion. The 0K dissociation onsets for the production of the CH 3 NH 3 + , CH 2 NH 2 + , and (CH 3 ) 2 CCH 2 NH 2 + ions have been determined to be 9.54±0.05, 9.647±0.025 and 9.90±0.1eV, respectively. Because the heat of formation of the CH 2 NH 2 + +t-C 4 H 9 products are established, we can use the measured onset of 9.647eV for this reaction to establish the neopentylamine ΔfH298°=−130.3±3.3 kJ/mol. This result is used in a group additivity scheme to estimate the neopentyl alcohol heat of formation as ΔfH298°=−315.5±4 kJ mol−1. Both of these results are strongly supported by a series of isodesmic reactions calculated at the G3B3 and CBS-APNO levels. This is the first reported experimental heat of formation of the neopentylamine and the first reported heat of formation of the neopentyl alcohol.