It is of practical significance to manufacture high-performance and durable semiconductor heterojunctions for photoelectrochemical (PEC) water splitting. Herein, hydrophilic polypyrrole and graphitic carbon nitride (g-C₃N₄) co-decorated ZnO nanorod arrays were synthesized as a photoanode by facile spin-coating and plasma-treatment methods. On the one hand, g-C₃N₄ nanosheets are modified on ZnO nanorod arrays to broaden the light-absorption range and suppress the recombination of photogenerated charges. On the other hand, the polypyrrole coating layer inhibits the dissolution and corrosion of ZnO nanorods and constructs a p–n heterojunction with ZnO to further promote the separation and transfer of photogenerated charge carriers. Furthermore, its hydrophilic surface provides a vast electrochemically active surface area for efficient charge/mass transfer. As a result, the as-prepared photoanode exhibits an enhanced PEC performance with a distinctly increased photocurrent and remarkably ameliorated stability in contrast to the ZnO photoanode. This research would provide an innovative perspective on the design of organic/inorganic semiconductor heterojunctions with excellent performance and stability for PEC water-splitting systems.