The effect of the CO2 content (up to 30%) on the methane catalytic combustion over a perovskyte-based monolith has been investigated at high pressure (up to 8 bar). Catalytic tests have been performed by varying the preheating temperature and the operating pressure. The CO2 adsorption over the catalytic surface has been evaluated through temperature-programmed desorption tests coupled to a kinetic model. Results show that the presence of CO2 retards ignition, shifting the ignition pressure at higher values. However, once ignition has been attained, the catalytic surface temperature increases upon an increasing CO2 content. These results have been explained by a double role of CO2: on one hand, it affects the ignition through adsorption over the catalytic surface, and on the other hand, it decreases the gas thermal diffusivity, thus reducing the velocity of heat removal from the surface.