We present the thermodynamic properties of ZrC (1− x ) N x ceramics at elevated temperature (0–1,000 K) and pressure (0–150 GPa) conditions, explored by density functional theory. We implemented the Debye–Grüneisen quasi-harmonic model in our calculations. In our investigation, we cover elastic constants, elastic moduli, compressibility, ductility/brittleness, hardness, sound velocities, minimum thermal conductivity, melting temperature, anisotropy indices, isothermal bulk modulus, heat capacities, entropy, Debye temperature, Grüneisen parameter, thermal expansion coefficient, and thermal pressure. We address the effect of the structural anisotropy and bonding nature of ZrC (1− x ) N x compounds on their thermal response to extreme conditions. Considering ZrC (1− x ) N x with the x in the range of 0.0, 0.25, 0.5, 0.75, and 1.0, ZrC 0.50 N 0.50 stands out in the response to the applied conditions. At higher temperatures, the thermal expansion of the ZrC 0.50 N 0.50 shows a smaller increase, which makes it a favorable candidate for coating material in cutting tools against commonly used ZrN and ZrC ceramics. Similar behavior is observed for the heat capacity by increasing pressure at higher temperatures, where a smaller reduction is observed. It could be interpreted as a more stable response regarding the application-specific design conditions.