UV/chlorine is an effective process for pollutant degradation in water treatment. It was reported that the concentrations of hydroxyl radical (HO^•) and chlorine radical (Cl) could rise significantly by adding TiO₂ in UV/chlorine. In this study, the degradation of ibuprofen (IBP), a frequently detected pollutant in aquatic environments, was investigated in the UV/chlorine/TiO₂ process. The pseudo-first-order kinetics rate constant for IBP degradation by UV/chlorine/TiO₂ was nearly 3-fold higher than the sum of the rate constant by UV/chlorine and UV/TiO₂. HO and Cl were the primary radicals and chlorine oxide radical (ClO) also participated in the degradation of IBP in UV/chlorine/TiO₂. The kinetic model was used to assess the effect of different influencing factors (chlorine, chloride, and bicarbonate dosage, and pH) on degradation kinetics and radical roles. Meanwhile, the probe experiment with nitrobenzene was performed to evaluate the reliability of the modeling results. The electrical energy per order (EE/O) was determined under varied chlorine and TiO₂ dosage, and the lowest EE/O of UV/chlorine/TiO₂ was obtained to be about 40% and 50% of that of UV/chlorine and UV/TiO₂, respectively. Toxic products could be generated during IBP degradation in all three processes, while less reaction time was needed for the removal of solution toxicity by UV/chlorine/TiO₂. When achieving IBP degradation by one order of magnitude, less disinfection byproducts were generated in UV/chlorine/TiO₂ compared with UV/chlorine both with and without 24 h post-chlorination. Furthermore, a chlorine-substituted product of IBP was detected, and both HO and Cl participate in the formation of this product based on density functional theory (DFT) study.