Nonequilibrium heat capacities of CO₂ are studied under the conditions of 4-temperature of oscillatory relaxation. There are used the model of anharmonic oscillator, generalized Trinor distribution and nonequilibrium Boltzmann distribution for harmonic oscillations. The nonequilibrium oscillatory heat capacities of CO₂ are obtained in the temperature range T, T₁, T₂, T₃ from 1000 K to 5000 K as calculation results.