Display omitted •Removal efficiency of iopamidol followed the order of UV/Cl2 > UV/H2O2 > .•UV/NH2Cl > UV/ClO2 > UV.•EE/O of iopamidol degradation followed the trend of UV/ClO2 > UV > UV/NH2Cl > UV/H2O2 > UV/Cl2.•The pH behaviors of UV-based AOPs upon iopamidol in 5–9 exhibited quite differently.•UV/Cl2 and UV/NH2Cl enhanced classical DBPs and I-THMs while UV/ClO2 and UV/H2O2 exhibited elimination effect.•The risk ranking of DBPs-related toxicity was UV/NH2Cl > UV/Cl2 > UV > UV/H2O2 > UV/ClO2. The UV-induced advanced oxidation processes (AOPs, including UV/Cl2, UV/NH2Cl, UV/ClO2 and UV/H2O2) degradation kinetics and energy requirements of iopamidol as well as DBPs-related toxicity in sequential disinfection were compared in this study. The photodegradation of iopamidol in these processes can be well described by pseudo-first-order model and the removal efficiency ranked in descending order of UV/Cl2 > UV/H2O2 > UV/NH2Cl > UV/ClO2 > UV. The synergistic effects could be attributed to diverse radical species generated in each system. Influencing factors of oxidant dosage, UV intensity, solution pH and water matrixes (Cl−, NH4+ and nature organic matter) were evaluated in detail. Higher oxidant dosages and greater UV intensities led to bigger pseudo-first-order rate constants (Kobs) in these processes, but the pH behaviors exhibited quite differently. The presence of Cl−, NH4+ and nature organic matter posed different effects on the degradation rate. The parameter of electrical energy per order (EE/O) was adopted to evaluate the energy requirements of the tested systems and it followed the trend of UV/ClO2 > UV > UV/NH2Cl > UV/H2O2 > UV/Cl2. Pretreatment of iopamidol by UV/Cl2 and UV/NH2Cl clearly enhanced the production of classical disinfection by-products (DBPs) and iodo-trihalomethanes (I-THMs) during subsequent oxidation while UV/ClO2 and UV/H2O2 exhibited almost elimination effect. From the perspective of weighted water toxicity, the risk ranking was UV/NH2Cl > UV/Cl2 > UV > UV/H2O2 > UV/ClO2. Among the discussed UV-driven AOPs, UV/Cl2 was proved to be the most cost-effective one for iopamidol removal while UV/ClO2 displayed overwhelming advantages in regulating the water toxicity associated with DBPs, especially I-THMs. The present results could provide some insights into the application of UV-activated AOPs technologies in tradeoffs between cost-effectiveness assessment and DBPs-related toxicity control of the disinfected waters containing iopamidol.