Irrigation has an important role in enhancing and stabilizing food production, especially in the less-developed countries of Africa. However the performance of most existed irrigation projects in developing countries are poor. Therefore this study was focused to evaluate the performance of Upper Quashini irrigation scheme using internal (process) performance indicators. Assessment was conducted by developing well-structured questioner and interviewing beneficiary farmers and key informants to identify key constraints encountered in utilizing the scheme. For technical evaluation of the scheme using performance indices, three farmers’ fields were selected each from the head, middle and tail-end water users. Primary and secondary data were collected from different literatures/documents and organizations, by physical field observation and actual field investigation. Measurements of discharge in the main and secondary canals of the irrigation scheme, determination of moisture contents of the soil before and after irrigation, determination of soil physical properties and measurement of depth of water applied to the fields were also carried out in the field. The application efficiency, conveyance efficiency, storage efficiency, deep percolation fraction, water delivery performance, maintenance indicators (sustainability and effectively of infrastructures) as well as overall management challenges were evaluated. The results indicated the conveyance, application, storage and deep percolation fraction of the irrigation scheme were found 62.05%, 49.1%, 94.7% and 50.9% respectively with an overall scheme efficiency of 30.46%.The delivery performance, effectiveness of infrastructure and sustainability of irrigated area were also found to be 49.6%, 49.3 % and 80% respectively. Over 83 % respondents confirmed the establishment of the project was important in saving labor and money than it was in traditional diversion of the river. Partly it was understood that the current scheme has improved the livelihood of the beneficiaries. On the other hand there was a great dissatisfaction of farmers found on right side of the river due to malfunctioning of secondary canal. Those farmers are totally not beneficial from the project. In general the overall performance of the scheme was not as it was expected as compared to the recommended standards due to layout problem, structural failure, sediment and poor overall management system.