High concentrations of H₂S are contained in unused industrial gases and biomass gasification gases, necessitating catalysts which are robust in the presence of H₂S to produce H₂ from them. Pure CeO₂ is known for its robustness, but rare earth oxide consumption should be reduced to improve sustainability. Herein, a stable dry reforming reaction is demonstrated over CeO₂/MgO under reaction conditions of 2000 ppm H₂S. A comparable catalytic activity to pure CeO₂ was exhibited by 5 mol% CeO₂/MgO despite its low loading of CeO₂. Further, no carbon deposition or impurity phases were formed in the catalyst after an 8-h reaction. Transmission electron microscopy revealed that MgO stabilized the CeO₂ nanoparticles under these reaction conditions. Also, kinetic analyses, infrared spectroscopy, and isotopic labeling studies suggested that the CeO₂-MgO interface strongly captures CO₂ and supplies it to the CeO₂ surface to accelerate the dry reforming reaction.