© ASCE.Catalytic ozonation is a promising advanced oxidation technique for the removal of contaminants from water and wastewater. Graphene oxide (GO) is an oxidized derivative of graphene which contains epoxide, hydroxyl, and carboxyl groups with high surface area, and is being recently used for effective adsorption of pollutants in aquatic environments. In our previous work, we modified GO with magnesium oxide (MgO) and demonstrated the high-rate adsorption of methylene blue (MB) by the synthesized nanocomposite (NC). In this study, our synthesized NC is applied as a catalyst for catalytic ozonation of phenol in a laboratory scale batch reactor. The results showed that the catalytic ozonation significantly improved the mineralization of phenol compared to that of ozonation without the catalyst. The impact of experimental variables on oxidation of phenol, particularly GO/MgO NC dosage and reaction time is investigated. A possible mechanism for the catalytic ozonation of phenol is also proposed. Our results show promising application of the proposed technology for the removal of various organic contaminants from wastewater.