Effective charge separation and transfer of photoinduced electron (e − )−hole (h + ) pairs in a perovskite photocatalyst, namely, SrTiO 3 (STO), are crucial factors for a highly effective and durable photocatalytic hydrogen evolution reaction (HER). Herein, we develop a highly efficient pathway based on a semiconductor−metal heterostructured photocatalyst, in which Ir-doped (STO) nanocubes loaded with Ag nanoparticles are prepared by two facile approaches for water splitting driven by visible-light irradiation. This strategy was easily accessible to highly enhanced photocatalytic HER activities by (i) Ir 3+ doping in the forbidden gap of STO nanocubes for broadening the light absorption wavelengths up to 730 nm and (ii) incorporating Ag nanoparticles for controlling the electron−hole transportation at the interface and developing active reaction sites. Remarkably, the as-synthesized Ag/Ir/STO showed apparent quantum efficiencies of up to 0.17% and 0.06% under UV light and 420 nm illumination, respectively, which are 7.4-, 2-, and 1.6-fold higher than those of bare STO, binary Ag/STO, and Ir/STO, respectively. It also possessed outstanding stability in the photocatalytic process after four cycling tests. This work provides a rational design of a metal cocatalyst−semiconductor channel for enhancing the photocatalytic HER under visible light.