Au/TiO₂-based systems with the right combination of electronic configuration, structural dynamics, and stability have recently attracted wide attention in photoelectrochemical (PEC) water splitting for hydrogen generation. Here, we used the masking effect of Au nanoparticles that were dewetted from sputtered Au thin films to fabricate TiO₂ nanowire arrays with restricted planar coalescence on flat nucleation layers. The well-spaced vertically aligned TiO₂ nanowires allowed for effective coating of another Au thin film by sputtering. A further thermal dewetting process led to a uniform distribution of Au nanoparticles along the nanowire surface. When this sample was used as a photoanode for PEC water splitting, significantly increased photocurrent density and improved PEC activity toward water oxidation were achieved. Systematic electrochemical and PEC characterization demonstrated that the dual functions of the dewetted Au nanoparticles in regulation and surface passivation of TiO₂ nanowires were indispensable for the efficient generation, transfer, and separation of photogenerated charge carriers and the consequential boosted PEC water oxidation performance.