Activated sludge process (ASP) has been widely used for the treatment of high organic load industrial wastewater. Toxic compounds (e.g phenol at high concentration) limit the application of ASP. In the present work, ASP preceded by anoxic selector was investigated for the treatment of phenolic effluents generated from a chemical and pharmaceutical industry. The parameters affect the process (phenol concentration, food to microorganism ratio (F/M), retention time and pH) were studied using batch and completely mixed activated sludge (CMAS) type reactor (with and without anoxic selector). The results showed that the maximum removal efficiency obtained by using batch process was 99.9% at 800 mg/l initial phenol concentration, F/M ratio of 0.579 (g COD/g MLVSS.d) and pH around 7. For CMAS only, the maximum applied phenol concentration was 2000 mg/l to yield effluent phenol concentration of 35 mg/l. For anoxic selector-CMAS, the maximum applied phenol concentration was 5500 mg/l to yield effluent phenol concentration of 0.01 mg/l. It was found that the performance of industrial wastewater treatment was significantly enhanced using anoxic selector. It is concluded that the use of properly designed anoxic selector prior to CMAS significantly improves the performance of the process and can tolerate much higher phenol concentration than that tolerated by the conventional CMAS. The application of the proposed system contributes to the establishment of technically viable solutions for water bodies pollution by phenolic wastewater.