The proper start-up period, as well as process performance verification, are essential for the successful operation of biological treatment systems. The objective of the study is to investigate experimentally the start-up process and operational performance of a sequence batch reactor (SBR) system used in treating automotive services oily wastewater generated from Hamdan Industrial Zone (HIZ) in Basrah governorate, south of Iraq. The study involved the analysis of different physiochemical parameters present in the wastewater. It results revealed that the start-up (or microbial acclimatization) period of the employed system is about 36 days. During this period the concentration of MLSS and MLVSS gradually increased over time to 5012 and 3285 mg/l, respectively. At the occurrence time of maximum MLSS occurrence, the achieved SVI was 72 ml/g. The SBR performance results, gathered by influent and effluent analyses, showed that the COD, BOD, and oil and grease removal efficiency values varied in the ranges (71.1- 75.1), (81.9- 85.0), and (66.7-68.4) %, respectively. The VSS, TSS, NBSCOD, and NBPCOD removal efficiencies vary in the ranges (57.5-81.2) (59.8-82.0), (63.8-66.5) and (53.8-75.5) %, respectively. When the SBR effluent concentrations of the BOD5, COD, TSS, and oil and grease were compared with their permissible limits of Iraqi regulations, it was noticed that all these parameters did not comply with their permissible limits. Based on the study findings, the SBR system used to treat oily wastewater generated by automotive services needs to be improved by adding innovative treatment technologies to comply the quality of treated wastewater with the standard specification regulations.