Using organic oxidation reactions to replace the oxygen evolution reaction is a promising approach for producing high-value organic products and hydrogen. Here, we report a photoelectrochemical benzyl alcohol oxidation system based on an α-Fe2O3 photoanode coated with a NiCo-layered double hydroxide (NiCo-LDH) cocatalyst. By adjustment of the relative content of Ni and Co in the NiCo-LDH, the optimized photoanode achieved a benzyl alcohol conversion efficiency of 99.1% and benzoic acid selectivity of 90.9%. Experimental studies revealed that the benzyl alcohol oxidation reaction proceeds via an indirect catalytic mechanism involving high-valence species of the NiCo-LDH cocatalyst. Co in NiCo-LDH reduced the formation energy barrier and oxidative capability of the high-valence species, thereby influencing the performance of the photoanode. This work provides insights into the crucial role of cocatalyst composition in organic reaction oxidation and contributes to developing various photoelectrochemical organic oxidation systems.