Fluorite CeO₂ nanorods (NRs) with tunable surface defects are successfully prepared via hydrothermal synthesis followed by post-calcination under different atmospheres. Impressively, the CeO₂ NRs obtained under mixed Ar and H₂ gas at 800 °C exhibit superior catalytic activity towards water oxidation under visible light (λ ≥ 420 nm), which is 10 times higher than that of CeO₂ NRs treated under air at 800 °C. Detailed characterization and theoretical analysis reveal that the rich surface defects including surface oxygen vacancies and Ce³⁺ ions are the origin of the enhanced water oxidation performance of the CeO₂ NRs treated under the reduced atmosphere.