The electrochemical stability and catalytic activity of palladium catalysts are key issues in polymer electrolyte membrane fuel cells (PEMFCs). Here, to take full advantage of the strong metal–support interaction (SMSI), Pd nanoparticles (NPs, ∼4.1 nm) were in situ reduced onto the TiO₂ surface of a TiO₂–C heterostructure by photo-generated electrons under light irradiation. By means of experimental characterization studies, electron transfer from the support (TiO₂–C heterostructure) to Pd NPs results in an electron-rich Pd surface and a downshift in the d-band structure. A photochemical strategy strengthens the SMSI effect and hence improves the catalytic activity and durability of the Pd catalyst. Compared with commercial Pd/C (Com. Pd/C, 10.0 wt%) and Pd/TiO₂ (22.0 wt%) catalysts, as-prepared Pd/TiO₂–C (7.2 wt%) shows excellent ORR activity with MA up to 0.16 A mg⁻¹_Pd at 0.9 V. The results demonstrate that for metal oxide supports with photocatalytic activity, the photochemical route is conducive to the formation of the SMSI effect between the metal and support, thus improving the activity and durability of the metal catalyst.