Experimental studies using mass spectroscopy, thermogravimetric analysis, in situ X-ray diffraction (XRD), and theoretical density functional theory calculations were carried out to investigate the mechanism of methane partial oxidation over a CaFe2O4 oxygen carrier. The XRD analysis revealed the formation of the calcium ferrite phases during methane reduction occurred the sequence CaFe2O4 -> O2-CaFe3O5 + Ca2Fe2O5 ->(O2-) FeO + Fe + CaO ->(O2-) Fe + CaO. Each of these phases was modeled using periodic density functional theory to study the activity of these phases for the reactivity with CH4, CO, and H-2 along with the adsorbed surface species to help elucidate the effect that phase changes during reduction have on the chemical looping products CO and H-2. Mass spectroscopic analysis revealed the formation of H2O and CO2 occurred prior to the formation of CO and H-2, and these products may be due to the removal of lattice oxygen bound in the discrete primary phase, which contributes to a small portion (similar to 16%) of the total transferable oxygen in the solid. The density functional theory (DFT) results suggest that the gaseous CO and H-2 are not thermodynamically favorable to react with the Ca2Fe2O5 where the release of CO and H-2 led to an increase in selectivity for these products. The DFT results suggest that some of the adsorbed atomic hydrogen combined to form adsorbed H-2 and then gaseous H-2 on the CaFe2O4 surface, while the carbon deposition and some adsorbed atomic hydrogen react to form the CaFe3O5 and Ca2Fe2O5 phases simultaneously. DFT simulations suggest that both the gaseous H-2 and adsorbed atomic H are less thermodynamically favorable to drive the deep reduction of Ca2Fe2O5 to CaO and Fe-0. The deep reduction of the calcium ferrite therefore favors the generation of syngas products (CO and H-2) through mechanisms of methane dehydrogenation and selective oxidation of carbon to CO. The significant difference in mechanisms for partial oxidation of methane to syngas with the CaFe2O4 carrier can be correlated to the differences in the oxide phases present during the reduction process, concentration of oxygen species, and bonding in the lattice structure.