AbstractPhoto‐thermal catalytic CO2hydrogenation is currently extensively studied as one of the most promising approaches for the conversion of CO2into value‐added chemicals under mild conditions; however, achieving desirable conversion efficiency and target product selectivity remains challenging. Herein, the fabrication of Ir‐CoO/Al2O3catalysts derived from Ir/CoAl LDH composites is reported for photo‐thermal CO2methanation, which consist of Ir‐CoO ensembles as active centers that are evenly anchored on amorphous Al2O3nanosheets. A CH4production rate of 128.9 mmol gcat⁻1h⁻1is achieved at 250 °C under ambient pressure and visible light irradiation, outperforming most reported metal‐based catalysts. Mechanism studies based on density functional theory (DFT) calculations and numerical simulations reveal that the CoO nanoparticles function as photocatalysts to donate electrons for Ir nanoparticles and meanwhile act as “nanoheaters” to effectively elevate the local temperature around Ir active sites, thus promoting the adsorption, activation, and conversion of reactant molecules. In situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) demonstrates that illumination also efficiently boosts the conversion of formate intermediates. The mechanism of dual functions of photothermal semiconductors as photocatalysts for electron donation and as nano‐heaters for local temperature enhancement provides new insight in the exploration for efficient photo‐thermal catalysts.