Hydrogen production through photocatalytic water splitting attracts great attention in fields of energy conversion. To improve the hydrogen evolution efficiency, narrowing the bandgap of photocatalysts by introducing dopant atoms is widely investigated for increasing light absorption. Herein, Mo-doped BaTiO₃ samples are synthesized by a traditional solid-state reaction method and all the samples are modified with Pt by a photo-reduction method. Compared with pure BaTiO₃, Mo doping into BaTiO₃ samples realizes the band-to-band visible-light absorption and shows remarkable improvement in hydrogen production efficiency. Under simulated sunlight irradiation and with 0.4 wt% Pt deposition, BaTiO₃ doped with 2 at% Mo exhibits a hydrogen evolution rate of 63 μmol g⁻¹ h⁻¹, about 2 times improvement in comparison to pure BaTiO₃ (35 μmol g⁻¹ h⁻¹). Further first-principles calculations based on density-function theory demonstrates an apparent downward movement of the conduction band minimum due to the coupling between the Ti 3d and Mo 3d states, leading to the significant bandgap narrowing and enhancement of the visible-light photocatalytic activity.