Reaction of non-stoichiometric SrFeO x (2.5=<x=<3.0) with carbon dioxide induced by high temperature and mechanical energy was investigated. The high-temperature reaction route was found to convert SrFeO x to a mixture of SrFe 1 2 O 1 9 and SrCO 3 at temperatures below 1128K under 0.98atm of CO 2 pressure. The mechanical reaction carried out at room temperature causes a complete decomposition of SrFeO x to strontium carbonate and hematite via a metastable ferric carbonate phase. We examined the phase transformations, the reaction kinetics and morphology of carbonated SrFeO x and compared the two processes.