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Metal–oxide interfaces play a crucial role in catalyzing CO2 conversion, while comprehensively decoupling interfacial catalysis is challenging due to their structural complexity. Herein, Rh/CeO2 catalysts, whose interfacial structures are finely tuned by altering the CeO2 morphologies and Rh particle sizes, were employed for CO2 hydrogenation. The results reveal that the density of interfacial oxygen vacancies that varies with the CeO2 morphologies determines the catalytic activity, while the product selectivity strongly depends on the nature of supported Rh species. With a decrease in Rh particle size, the weakened metallicity results in the suppression of the Sabatier reaction and thus the low CH4 selectivity. Meanwhile, the enhanced reverse water–gas shift process that is more easily catalyzed than the Sabatier reaction contributes to the promotion of catalytic CO2 efficiency. Interestingly, the CH4 selectivity increases with the reaction temperature rise at fine Rh particles, which could be ascribed to the enhanced H-spillover effect at high temperatures. Spectroscopic results confirm CO2 hydrogenation proceeding through a redox mechanism to generate an adsorbed CO intermediate that either is further hydrogenated into CH4 with strong CO adsorption capacity/H-spillover effect or desorbs directly into CO.