Since formaldehyde is considered to be a potential risk for human health, its emission must be eliminated in an effective way. In this study, anatase TiO₂ particles with silver nanoparticles were doped on wood substrates through a two-step method and used as a photo-catalyst for formaldehyde degradation. The effect of Ag dopant on the formaldehyde degradation of the TiO₂-treated wood was investigated. The results showed that the formaldehyde response of the TiO₂ film was drastically improved by doping with Ag nanoparticles under visible-light irradiation. In this heterostructured system, because the Fermi level of Ag was lower than the conduction band of TiO₂, Ag nanoparticles can act as electron scavenging centers to cause electron and hole pair separation, leading to enhanced photo-catalytic activity of TiO₂.