This work puts forward an exploration of a new ternary ZnCoV–layered double hydroxide (ZnCoV–LDH) as a highly efficient oxygen evolution co-catalyst to enhance the photoelectrochemical (PEC) water splitting performance of BiVO₄ photoanode. ZnCoV-LDH nanosheet was prepared by a fast and simple electrodeposition method. Compared to the bare BiVO₄, the composite photoanode showed a 370-mV cathodic shift in onset potential and an enhancement in photocurrent density by a factor of around 4, which delivering 2.7 mA cm⁻² at 1.23 V versus a reversible hydrogen electrode. In addition, the modified electrode was of greater steadiness for water oxidation. It is postulated that the enhanced PEC performance results from the efficient utilization of photogenerated holes in water oxidation due to the improved oxygen evolution reaction (OER) kinetics in the presence of the ZnCoV-LDH cocatalyst. More importantly, the role of each component in the electrocatalyst was also explored, in which Co species provide active sites to capture photogenerated holes for the water oxidation reaction while Zn species serve as structural support. It was found that the introduction of strongly electron-withdrawing V⁵⁺ can not only facilitate the in-situ formation of highly active Co³⁺ species for the OER, but can also adjust the electronic conductivity, thereby leading to the improved intrinsic activity and accelerated OER reaction kinetics. This work provides not only a demonstration of a novel and promising co-catalyst for PEC water splitting, but also a facile method for the rational design other hydroxide-based materials.