Highly conductive silver (Ag) film on poly(ethylene terephthalate) (PET) substrate was prepared by using room-temperature sinterable silver nanoparticle (AgNP) ink having TiO2 nanoparticles as photodecomposition catalysts. AgNP-40T ink having TiO2 nanoparticles (1 wt %) successfully produced Ag film with a conductivity up to 5.2% of that of bulk silver, after ultraviolet (UV) irradiation for 1 h. The photodecomposition of poly(N-vinylpyrrolidone) (PVP) ligands by TiO2 during UV irradiation might contribute to facile room-temperature sintering of AgNP-40T ink.