To enhance the performance of photocatalytic CO₂ reduction, the development of suitable cocatalysts represents an effective strategy. Cocatalysts can interact with photocatalysts to improve light absorption capabilities and facilitate the separation and transfer of photogenerated electrons and holes. Moreover, they provide highly active surface sites that promote the adsorption and activation of CO₂, which leads to acceleration of photocatalytic reduction. Herein, WO₃ is employed as a cocatalyst to promote the CO₂ photoreduction performance of a g-C₃N₄-TiO₂ heterojunction through a facile and scalable calcination method. In pure water, optimal WO₃/g-C₃N₄-TiO₂ (WCT) delivers high selectivity CO and CH₄ formation of 48.31 µmol·g⁻¹ and 77.18 µmol·g⁻¹ in the absence of a sacrificial reagent and extra photosensitizer, roughly 13.9 and 45.7 times higher than that of g-C₃N₄-TiO₂ (CT). WO₃ can strongly interact with g-C₃N₄-TiO₂ electronically, guiding electrons across the interface to the surface. The oxygen vacancies in WO₃, as electron-enriched centers, not only enhance charge separation and form efficient charge transfer channels but also capture photogenerated electrons to suppress charge recombination. This strong interaction and oxygen vacancies in WO₃ jointly improve photocatalytic CO₂ reduction activity and selectivity, offering a feasible way to design efficient cocatalysts.