Abstract In this work, the degradation of chlorimuron-ethyl, which belongs to the class of sulfonylurea herbicide, was performed by Fenton, photo-Fenton and ozonation. At the used experimental conditions, photo-Fenton degradation was influenced by the initial H2O2 and Fe2+ concentration. In the case of its degradation by ozonation, the best results were achieved when ozone was combined with UV and H2O2. Among the studied AOPs, photo-Fenton presented the best result concerning mineralization and chlorimuron-ethyl degradation, achieving degradations higher than 85% after 90 min of reaction. Based on the obtained results, the photo-Fenton system can be an important technique to be applied in the treatment of wastewater containing this pesticide.