The present work focuses on the performance of Fenton, sono-Fenton, and sono-photo-Fenton processes for the oxidation of phenol present in aqueous solution. The effects of H2O2 concentration, Fe2+ concentration, pH, and initial phenol concentration on the oxidation of phenol were studied. The optimum Fe2+ and H2O2 concentrations for the Fenton process were 45 and 800mg/L, respectively. For the sono-Fenton process, the optimum Fe2+ and H2O2 concentrations were 30 and 800mg/L, respectively. The optimal conditions for the sono-photo-Fenton process were found to be 20mg/L of Fe2+ and 700mg/L of H2O2. The optimum pH was found to be 3 for the processes investigated in the present study. The analysis of results showed that the sono-photo-Fenton method reduced the Fe2+ concentration by 30-50% and the H2O2 concentration by 12.5%. It was found that the sono-photo-Fenton technique showed better performance than the Fenton and sono-Fenton processes for the oxidation of phenol. A lumped kinetic model was used to predict the chemical oxygen demand reduction and the model was found to fit the data. Synergistic effects of sono, photo, and Fenton processes on the degradation of phenol are presented. The sono-photo-Fenton technique showed better performance than the Fenton and sono-Fenton processes for the oxidation of phenol. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.