Assessing irrigation scheme performance is vital to evaluate the socio-economic impacts of irrigation practices, identify gaps and improve system performances. Despite several irrigation schemes are constructed in Somali Regional State, their performance was not assessed. Therefore, this study was carried out to evaluate the performance of Kullen Irrigation Scheme using 12 indicators. Primary data through field measurements and secondary data from different reports and institutions were gathered. Key informant interview and informal discussions with farmers were also carried out to collect information related to their perceptions and institutional supports. CROPWAT 8.0 model and GIS software were used to analyze the data. The results showed that the scheme irrigates only 57% of the designed command area due to large part of the command area is covered by Prosopis Juliflora, which negatively affected production and productivity of both crops and livestock. The scheme is relatively well performing with overall efficiency of 48%. The higher average values of the outputs per unit area also encourages farmers to invest more in irrigation activities. Additionally, the average values of the outputs per unit water consumed and water supply are relatively high because of growing market-oriented vegetables. A relative water supply of 1.70 indicates that water supplied was enough to meet the demands, while water delivery capacity of above 1 indicates the scheme is capable of delivering the required peak water demand. However, the relative irrigation supply of 1.73 showed that much of the water is lost through conveyance and applications. The gross return on investment was high (1.08) due to growing market-oriented crops, and presence good market opportunities around Dire Dawa, Harar and Jigjiga areas. However, there is no revenue generated from the irrigation scheme and beneficiaries’ contributions in O&M were negligible. Consequently, the regional government spends 35 to 50 million every year all r O&M activities. To increase the productivity and ensure sustainability of the scheme, however, farmers are also requested improvement in the extension services (e.g., fertilizer and improved crop varieties), provision of training for WUA and clearing of Prosopis trees. Key words: Irrigation, performance indicators, sustainability, groundwater