Novel nanoarrays composed of inorganic–organic CdS@g-C₃N₄ core–shell nanorods were fabricated via a simple hydrothermal treatment and heating process. The samples were characterized by XRD, FESEM, TEM, XPS, FTIR, UV-vis and photoelectrochemical (PEC) measurements. We find that both PEC performance and stability against light illumination of the CdS@g-C₃N₄ CSNRs are significantly enhanced compared with pure CdS NRs. The photocurrent density of the CdS@g-C₃N₄ CSNRs reaches up to 1.16 mA cm⁻², which is 2.5 times higher than that of pure CdS NRs under the same conditions. More importantly, after 3600 s continuous illumination, the CdS@g-C₃N₄ CSNRs are quite stable and more than 85% of the initial photocurrent is sustained, while the photocurrent of CdS NRs decays to 20% of the initial value. Finally, a possible mechanism for the enhanced PEC performance and stability of the CdS@g-C₃N₄ CSNRs heterostructure is proposed and discussed systematically based on our experimental results.