The treatment of a petroleum refinery wastewater is studied using a bench scale UV/H2O2 photoreactor in batch mode. The average initial total organic carbon (TOC) concentration is 42mg/L. Moreover, the initial H2O2 concentrations are 345, 690, and 1023mg/L for initial H2O2/TOC molar ratios of 2.9, 5.8, and 8.6, respectively. The results reveal that the highest treatment efficiency of 78.38% for the removal of TOC from the refinery wastewater using the bench scale UV/H2O2 photoreactor occurs at the reaction time of 45min and a pH of 5.0. A three-factor analysis of variance (ANOVA) is used to verify the statistical significance of the initial H2O2/TOC molar ratio, reaction time, and pH on the bench scale UV/H2O2 photoreactor. Furthermore, the respirometry analysis shows that the pretreated refinery wastewater by the UV/H2O2 process is inhibitory on activated sludge (AS) microorganisms. Thus, the UV/H2O2 process is found to be currently not suitable as a pretreatment process for refinery wastewater treatment at these operational conditions.