The performance of a plug flow electrocoagulation reactor for the treatment of cattle abattoir (slaughterhouse) wastewater was investigated. A cylindrical iron reactor was operated as a cathode at a recycling batch mode while three iron rods located at the center of the reactor were used as an anode. The effects of different parameters, including the current density, the supporting electrolyte dosage (Na2SO4), the wastewater recirculation rate, the initial pH and the polyelectrolyte addition were also evaluated. In order to achieve a high removal efficiency, the Electro-Fenton process was also evaluated by adding H2O2, of various concentrations. When the abattoir wastewater was subjected to the Electro-Fenton process, the best result regarding the removal of COD was obtained as 90% with an electrical energy consumption of 0.2 kWh/L. The experimental results reveal that the direct dischargeable effluent, according to Turkish legislation, was obtained in this study. In conclusion, the electrochemical reactor designed for this purpose is effective for the removal of COD from wastewater.