An oil refinery is one industry that introduces large amounts of toxic phenol in receiving waters annually. Hence, the aim of this study was phenol removal from oil refinery wastewater by a natural treatment system of a stabilization pond. In this study, a pilot-scale pond volume, hydraulic load, and hydraulic retention time were 200 L, 40 L/day and five days, respectively. Influent concentration of phenol was 100-400 mg/L. Responses of the process were NH₃, PO₄, phenol, TCOD, SCOD, TBOD, SBOD, and pH. The results showed that increasing phenol concentration and decreasing temperature have negative effects on system efficiency. Maximum removal of NH₃, PO₄, phenol, TCOD, SCOD, TBOD, and SBOD were 61.08, 70.09, 93.58, 80.18, 78.89, 78.7, and 76.84% in high temperature, respectively. Maximum efficiency of wastewater treatment system was obtained in phenol concentration at 100 mg/L. Also, anaerobic stabilization ponds are cost-effective options with simple operation that can be employed for the treatment of phenol content of oil refinery wastewaters.