A novel strategy was designed to prepare Ag cluster-doped TiO2 nanoparticles (Ag/TiO2 NPs) without addition of any chemical reducing agent and/or organic additive. A defect-rich TiOx species was generated by laser ablation in liquid (LAL) of a Ti target. The silver ions could be reduced and deposited on the surface of TiO2 NPs through the removal of oxygen vacancies and defects; the TiOx species evolved into anatase NPs in a hydrothermal treatment process. The derived Ag/TiO2 NPs are approximately 25 nm in size, with narrow size distribution. The Ag clusters are highly dispersed inside TiO2 and less than 3 nm in size. The doped amount can be tuned by changing the concentration of Ag+ ions. The as-synthesized Ag/TiO2 NPs display improved photocatalytic efficiency toward pentachlorophenol (PCP) degradation.