The spectroscopic constants for the ground electronic state of N₂⁺ and for several low-lying excited electronic states are used to obtain the Hulburt-Hirschfelder potential energy curves for these states. The potential energy curves are then used to calculate the second virial coefficient and its derivatives for each state. These results are degeneracy averaged and used to calculate the heat capacity as a function of temperature to high temperatures such as those associated with shuttle re-entry. The heat capacity results are compared with results obtained using the partition function method.