Performance evaluation of irrigation system is essential to evaluate how far the goals and objectives set out at the time of project formulatio n of the system have been achieved. Efficient operation and management for small -scale irrigation systems play a significant role in the sustainability of irrigated agriculture. Nowadays, non -uniform water distribution at the head, middle, and tail of irrigation users, structural failure, loss of water at the earthen canal, water logging at irrigated lands of some farmers, and the irrigation system is not effective in Deremo small -scale irrigation scheme. This study was intended to evaluate the scheme performance using efficiency indicators, organizational setup indicators, maintenance indicators, farmers' perceptions, and assess the water delivery, on -farm water management, and organizational setup performances of the small-scale irrigation scheme. Primary data through field measurements, household surveys, key informant interviews, and group discussions, and secondary data from different reports, standards in FAO, and legal office data were taken. We applied GIS software, and CROPWAT 8.0 model, to analyze the data. The result of this study showed that the conveyance efficiency was 84.6%, the application efficiency was 75%, the storage efficiency was 31% and the overall efficiencies of Deremo SSI scheme was 63%. The effectiveness of infrastructures is that 36% of initially installed infrastructures were non-functional. The irrigated area of the scheme was decreased by 40% compared with the planned area. Questioners replied that the major problems of the scheme were inefficient maintenance, water theft or unauthorized canal breaching, water shortage, and conflict on water utilization, and lack of established Water user Association at the scheme. Generally, the overall performance of the irrigation scheme is considered medium level. So, it is crucial to establish a water user association, create road access, lined canal extension, routine maintenance, and creating awareness for the users to achieve good performance of the scheme. Keywords: Deremo, Performance, Efficiency, Evaluation, Irrigation.