The efficiency of several commercial and laboratory catalysts in the catalytic ozonation of a simulated phenolic wastewater was tested. Experiments involving three ceria-based catalysts prepared in our laboratory, namely, Co-Ce-O (70/30), Ag-Ce-O (70/30), and Mn-Ce-O (70/30), were compared with those involving commercially available catalysts, namely, G66A (CuO-ZnO/Al2O3), N-150 (Fe2O3-MnOx), SG2216 (CuO-MnOx/Al2O3), and N-140 (CuO-MnOx). Of these, Mn-Ce-O (70/30) was found to be an interesting alternative because 80% of the total organic carbon was removed after 120 min of oxidation. The biodegradability of the simulated wastewater was assessed by measuring the ratio BOD5/COD before and after each treatment. Single and catalytic ozonation over Ag-Ce-O led to a less biodegradable effluent, whereas the rest of the catalytic systems truly enhanced the biodegradability of the simulated wastewater. Trends in the concentrations of some intermediates and the pH profiles were also analyzed for single and catalytic ozonation over Mn-Ce-O (70/30).