The effects Of CO2 partial pressure on oxidative methane coupling over a Li/MgO catalyst were studied under low conversion conditions in a flow reactor. Methane to oxygen ratios from 0.5 to 35 and temperatures from 973 to 1073 K were used in the experiments and modeling. Varying flow rates Of CO2 were mixed with the methane and oxygen prior to the reaction. Results indicate that CO2 has a poisoning effect on both carbon oxides (CO and CO2) and C2 hydrocarbon (C2H4 and C2H6) formation rates, while selectivity to the C2 hydrocarbon was not significantly affected. The apparent activation energy increased with CO2 partial pressure in the feed. Results also indicate that a small amount of methane reacts with carbon dioxide to produce carbon monoxide. Empirical rate expressions and rate expressions rigorously derived from proposed mechanisms were obtained. The rate expressions agree well with the measured rates and also predict the observed trend in apparent activation energy.