The present paper deals with the treatment of wastewaters generated from Al-Dewaniya petroleum refinery plant by Electro-Fenton process in a batch electrochemical reactor using porous graphite as anode and cathode materials. Effects of operating factors such as current density (5-25mA/cm2), FeSO4 concentration (0.1-0.7mM), NaCl addition (0-2g/l), and time (15–45min) on the efficiency of the chemical oxygen demand (COD) removal were studied. The results revealed that FeSO4 concentration has the main effect on the efficiency of COD removal confirming that the Electro-Fenton process was governed by reaction conditions in the bulk of solution between ferrous ions and H2O2 not upon the electrochemical reactions on the surface of electrodes. Parametric optimization was carried out using response surface methodology (RSM) combined with Box–Behnken Design (BBD) to maximize the removal of COD. Under optimized operating conditions: FeSO4 concentration (0.7mM), current density (25 A/cm2), and time (45 min) with no addition of NaCl, the removal efficiency of COD was found to be 95.9% with an energy consumption of 8.921kWh/kgCOD.