The kinetics of the thermal decomposition of CaCO₃ is significantly influenced by atmospheric and self-generated CO₂ due to the reversibility of the reaction. More detailed understanding of this well-known phenomenon is desired for establishing an effective Ca-looping in the CaO–CaCO₃ system for energy storage and CO₂ capture. This article shows the universal kinetics of the thermal decomposition of CaCO3 over different temperatures and partial pressures of CO₂ (p(CO₂)) with the aid of an accommodation function (AF) composed of p(CO₂) and equilibrium pressure. An analytical form of AF with exponents (a, b) was derived based on the kinetic considerations for the consecutive elementary steps of the surface nucleation and interfacial reaction. The overall kinetics of the thermal decomposition of CaCO₃ were described universally over different temperatures and p(CO₂) values by introducing the AF, in views of the isoconversional and isothermal kinetic relationships using the extended Friedman and experimental master plots, respectively. The universal kinetic description was extended to the kinetic modeling based on the physico-geometrical consecutive process comprising an induction period (IP), a surface reaction (SR), and a phase boundary-controlled reaction (PBR). The proposed kinetic approach enables parameterizing the CO₂ effect via the optimized (a, b) and tracking changes in the CO₂ effect as the physico-geometrical reaction step advanced from IP to PBR via SR. Furthermore, using the established universal kinetic description across different temperatures and p(CO₂) values, a challenge was set to quantify the contributions of atmospheric and self-generated CO₂ on the kinetics.