In summary, the development of the Au/BiVO4/WO3 ternary junction demonstrated significant advancements in photoelectrochemical performance through a series of straightforward fabrication processes. BiVO4 NPs were applied to hydrothermally grown WO3 nanobricks via a drop-casting method, followed by the reduction of Au NPs onto the BiVO4/WO3 heterostructure through the electrochromic activation of WO3. The systematic optimization of BiVO4 deposition on FTO conductive glass and WO3 further enhanced the photoanode's performance, underscoring the critical role of morphological and optical features. The superior photocurrent achieved with this novel nanocomposite was attributed to several factors: 1) strong light absorption, owing to the BiVO4 photosensitizer and the surface plasmon resonance (SPR) effect of Au NPs; 2) reduced charge recombination, leading to more efficient charge separation due to the Schottky barrier at the metal/semiconductor interface; and 3) rapid interfacial charge kinetics resulting from the high conductivity of WO3. Thus, this study provides insights into the role of plasmonic metals in enhancing the efficiency of semiconductor-based heterojunctions and offers a novel, scalable approach for optimizing advanced PEC system design.