The design and performance evaluation of Kotebe wastewater treatment was carried out. The treatment plant is a Waste Stabilization Pond (WSP) comprised of two anaerobic, three facultative, two maturation and two polishing ponds configured in parallel. Samples were taken at input and output points for each pond units over a period of five months, from November 2017 to March 2018.The samples were analyzed according to relevant standard methods. The results obtained from the samples taken in different time showed that the average wastewater temperatures for the influent and effluent were 20.9oC and 19.9oCrepectivelly.The values of hydrogen power (pH) and dissolved oxygen (DO) is increased along the ponds series. The average overall removal efficiency of the treatment ponds for TSS , total nitrogen, total phosphorus were 56% , 29.1 % and 33.3%, while the overall efficiency of COD was 79%. The BOD of effluent of the WSP has been reduced from 391mg/l to 136mg/l, indicating a 65% removal. On other hand, a Faecal Coli form (FC) count of the influent and effluent were 1330 FC/100ml and 1056FC/100ml, which was 20.6% FC removal. A total coli form (TC) count of the influent sample showed 1590TC/100ml, whereas the effluent gave 1322TC/100ml which was 16.9% removal level. The waste water treatment plant does not comply the requirement of 80 mg/L BOD standard of Ethiopian Environmental Protection Agency (EEPA,2003) and 1000 FC/100ml of Fecal coli form Standard set by WHO. It was concluded that the effluent from the WSP is therefore unsuitable for discharge to the environment. The average wastewater flow to the treatment plant was measured and found 6800 m3/day which is higher than the design flow of 2000m3/day. And hence it is concluded that the plant is running over the design capacity.