In the present study, an anaerobic continuous stirred tank reactor (ACSTR) with consortium of mixed culture was operated continuously for a period of 110 days. The experiments were performed with three different hydraulic retention times and by varying initial phenol concentrations between 100 to 1000 mg/L. A maximum phenol removal was observed at a hydraulic retention time (HRT) of 4 days, with an organic loading rate (OLR) of 170.86 mg/L.d. At this condition, phenol removal rate of 89% was achieved. In addition, the chemical oxygen demand (COD) removal corresponds to phenol removal. Additional operating parameters such as pH, MLSS and biogas production rate of the effluents were also measured. The present study provides valuable information to design an anaerobic ACSTR reactor for the biodegradation of phenolic wastewater