Photoelectron photoion coincidence (PEPICO) spectroscopy has been used to investigate the dissociation dynamics of the cobalt tricarbonyl nitrosyl ion, CO(CO)(3)NO+. The ionization energy of CO(CO)(3)NO was measured from the threshold photoelectron spectrum to be 8.33 +/- 0.04 eV. The dissociation of the molecular ion proceeds by two sequential carbonyl-loss steps and then a parallel carbonyl- or nitrosyl-loss step. The first two reactions were observed to be slow (lifetimes in the microsecond range). By simulating the resulting asymmetric time-of-flight peak shapes and the relative ion abundances (breakdown curves), 0 K onsets for the following fragment ions were determined: CO(CO)(2)NO+, 9.28 +/- 0.02 eV; CoCONO+, 10.43 +/- 0.02 eV; CoNO+, 12.00 +/- 0.02 eV; CoCO+, 12.07 +/- 0.02 eV. Combining these onsets with the experimental adiabatic ionization energy Of CO(CO)(3)NO+, the three cobalt-carbonyl bond energies in Co(CO)(3)NO+ (x = 1-3) were determined along with the cobalt-nitrosyl bond energy in CoCONO+. Using a literature value for the [Co-CO](+) bond energy, the 0 K heats of formation of the above-mentioned molecular and fragment ions and of the neutral compound, CO(CO)(3)NO, were determined. Using these thermochemical data, the cobalt-nitrosyl bond energies were also derived for Co(CO)(3)NO+ and CoNO+. The latter is in good agreement with a theoretical literature value, while the first one explains why there is no observable NO loss from the molecular ion, CO(CO)(3)NO+. Room-temperature values of the heats of formation are also given using the calculated harmonic frequencies.