Photocatalytic hydrodenitrogenation of aromatic cyanides has been carried out on TiO₂ loaded with Pd nanoparticles (Pd–TiO₂) in the presence of ethanol as a hydrogen source. Photoirradiation of Pd–TiO₂ at λ > 300 nm in ethanol containing aromatic cyanides successfully produces the corresponding toluene derivatives and triethylamine with almost quantitative yields. Photoexcited Pd–TiO₂ catalysts promote oxidation of ethanol and reduction of protons, producing acetaldehyde and hydrogen atoms on the surface of Pd particles (H–Pd species). Aromatic cyanides undergo hydrodenitrogenation via consecutive reactions involving hydrogenation by the H–Pd species and condensation with aldehydes. The catalytic activity strongly depends on the amount of Pd loaded. The catalyst containing 2 wt% Pd, with a relatively low Schottky barrier height at the Pd–TiO₂ heterojunction and a large number of surface Pd atoms, exhibits the highest denitrogenation activity.