The capability to activate methane at mild temperature and facilitate all elementary reactions on the catalyst surface is a defining characteristic of an efficient catalyst especially for the direct conversion of methane to ethylene. In this work, theoretical calculations are performed to explore such catalytic characteristic of an IrO₂ (110) surface. The energetics and mechanism for methane dehydrogenation reactions, as well as C–C coupling reactions on the IrO₂ (110) surface, are investigated by using van der Waals-corrected density functional theory calculations. The results indicate that a non-local interaction significantly increases the binding energy of a CH₄ molecule with an IrO₂ (110) surface by 0.35 eV. Such an interaction facilitates a molecular-mediated mechanism for the first C–H bond cleavage with a low kinetic barrier of 0.3 eV which is likely to occur under mild temperature conditions. Among the dehydrogenation reactions of methane, CH₂ dissociation into CH has the highest activation energy of 1.19 eV, making CH₂ the most significant monomeric building block on the IrO₂ (110) surface. Based on the DFT calculations, the formation of ethylene could be feasible on the IrO₂ (110) surface via selective CH₄ dehydrogenation reactions to CH₂ and a barrierless self-coupling reaction of CH₂ species. The results provide an initial basis for understanding and designing an efficient catalyst for the direct conversion of methane to ethylene under mild temperature conditions.