Surface decoration of noble-metal cocatalysts on graphitic phase carbon nitride (g-C₃N₄) with high efficiency and trace content for water splitting is exciting but difficult to achieve. Herein, we report the anchoring of Au and metallic/oxidized Pt nanoparticles (NPs) on g-C₃N₄ as cocatalysts via a photoreduction process for enhancing photocatalytic H₂ production. Au NPs are preferentially decorated on g-C₃N₄, which can control the formation of metallic/oxidized Pt complex species. The well dispersed Au and metallic/oxidized Pt NPs improved the light-harvesting and the photo-generated carrier separation of g-C₃N₄. G-C₃N₄ sequentially decorated with Au (0.3 wt%) and metallic/oxidized Pt (0.3 wt%) cocatalysts, exhibited the highest and stable H₂ evolution rates of 2560 and 139 μmol h⁻¹ g⁻¹ under simulated sunlight and visible light (λ ≥ 420 nm) irradiation, respectively, compared to the samples that are simultaneously and sequentially decorated with the same content of Pt and Au on g-C₃N₄. The enhanced photocatalytic activity is attributed to the synergistic effect of Au and metallic/oxidized Pt cocatalysts, i.e., the effective localized surface plasma resonance coupling between Pt and Au NPs, as well as electron-sink function of metallic Pt, which promote the generation and transfer of more carriers from g-C₃N₄ to the Pt species, in addition to the superior hydrogen evolution capacity of metallic and oxidized Pt. This work maximizes the performance of noble-metal cocatalysts with minimized content and provides the possibility of realizing efficient solar-to-fuel conversion.