Threshold photoelectron-photoion coincidence spectroscopy was used to investigate the dissociation of the 1-chloroadamantane ion (C10H15-Cl+). The product of Cl loss reaction, 1-C10H15+, was the only fragment ion at experimental photon energies below 13.0 eV. Through the simulation of the metastable time-of-flight distributions of the 1-C10H15+ ion and the breakdown diagram, the 0 K appearance energy of 1-C10H15+ was determined to be 10.10 +/- 0.02 eV. Using this result and the IE value of 1-C10H15Cl, 9.30 +/- 0.10 eV, the dissociation energy of the Cl loss reaction was determined to be 0.80 +/- 0.10 eV. Using the known heats of formation of C10H15Cl and Cl, the 298 and 0 K heats of formation of the 1-C10H15+ ion were obtained to be 679.2 +/- 3.2 and 731.9 +/- 3.2 kJ/mol, respectively.