© 2017 Elsevier B.V. Solid oxide fuel cell (SOFC) systems provide efficient and clean power. Chromium poisoning is known to deteriorate the performance of the SOFC cathodes such as La1−xSrxCoO3 (LSCO) due to the formation of undesired products. We identify the reaction products when LSCO is in a CrO3 and O2 atmosphere using first principle thermodynamics, with the assumption that gas-phase CrO3 is the Cr source. Our results correctly identify SrCrO4 as the primary Cr poisoning product as observed in experiments and also provides temperature-pressure regimes under which Cr poisoning effects may be avoided.