The objective of this paper is to evaluate the treatment and biogas production efficiency of the full scale UASB reactor (with re-aeration systems) owned by St. George Brewery is situated in Addis Ababa. The waste water treatment system consists of a preliminary treatment unit, influent tank pit, equalization tank, UASB reactor and a re-aeration treatment unit. The treatment system collects approximately 1250 m3 waste water per day with organic loading rate of 3.7 kg COD /m3day. Waste water samples were collected at the inlet and outlet of each treatment system and analyzed for pH, biochemical oxygen demand (BOD), total suspended solids (TSS), total ammonia nitrogen (NH4-N), sulfide (S2-), sulfate (SO42-), nitrate nitrogen (NO3-N), Total Nitrogen (TN), Electrical conductivity (EC), chemical oxygen demand (COD), Total Phosphorus (TP) and orthophosphate (PO43-) between November 2012 and April 2013. This was done to determine the efficiency of the waste water treatment system to investigate if the final effluent discharged from the system to nearby river complies with the Ethiopian Environmental Protection Authority (EEPA) standards. The percentage removal efficiency of the waste water plant were 94.70 % (BOD5), 92.20 % (COD), 85.30 % (S2-), 87.30 % (TSS), 48.90 % (TDS), 44.98 % (NO3-N), 42.70 % (EC), 15.15 % (NH4-N), 10.30 % (TN), 9.25 % (TP), 6.61 % (PO43-) and 8.54 % (SO42-) respectively.The study revealed that TP, PO43-, EC, TSS and BOD5 of the final effluents exceeded the EEPA guidelines;however PH, temperature, TN,NH4-N,NO3-N, S2-, SO2-,TDS and COD could be discharged into nearby river without causing water pollution. The mean cumulative biogas production for the digestion of the brewery waste water in the UASB reactor was 487 Nm3/day and composed of methane (CH4) 82.85 %, carbon dioxide (CO2) 9.73 %, Oxygen (O2) 0.018 %, trace gases (mainly N2 and CO) 7.3 % and hydrogen sulfide (H2S) 0.11 %. The overall removal efficiency of the plant was generally Very good. Integrating the waste water treatment system with aerobic fluidized bed reactor is promptly important in order to achieve effective performance and to meet discharge limits requirements of treated effluent into surface water. Keywords:Treatment, Performance Efficiency, St. George Brewery, Waste water, Biogas