A solid oxide fuel cell (SOFC) plays a significant role in converting chemically stored energy to electrical energy by using clean and renewable fuels, such as H₂ and CO. The LSFCr (La_0.3Sr_0.7Fe_0.7Cr_0.3O₃) perovskite is one of the few materials that is especially efficient and stable as a reversible SOFC (RSOFC) by performing not only the direct fuel cell reaction to generate power but also the CO₂ conversion back to CO. Many surface chemical reactions were studied for different perovskites, but the CO₂ reduction to CO at gaseous conditions has been reported for only a few materials. Unfortunately, for the LSFCr perovskite the precise atomic structures during mechanism of CO₂ electrolysis is unknown. This study identifies among many adsorption modes for CO₂ on the LSFCr surface the preferred active site and a suggested mechanism for the reaction using density functional theory (DFT) with nudged elastic band (NEB) tools. Surprisingly, the mechanism involves a stable, linear O–C–O angle during adsorption of CO₂ and bending of the angle is achieved only during the transition state. The results demonstrate the importance of oxygen vacancies in the catalytic process, as well as the importance of a Cr dopant in the reduction despite the direct bonding of CO₂ to Fe atom. Our results on the necessity of a particular oxygen vacancy concentration for the chemical reaction is supported by our thermogravimetric analysis (TGA) measurement.