Irrigation scheme performance assessment is vital to evaluate the impacts of irrigation practices and to identify performance gaps. The principal objective of this study was to evaluate the performance of Dinsira irrigation scheme using internal indicators in upper Dinsira irrigation scheme and assessment of institutional and support services so as to recommend appropriate measures to improve the scheme management and performance. Primary data collection includes flow measurement in the canal by current meter and partial flume at field canal; soil data (moisture content, bulk density, field capacity measures, PWP and available water depth in the root zones) were sampled and analyzed in laboratories. For bulk density and moisture determination field surveys and group discussions among the farmers and Water User Associations (WUAs).From house hold survey 539 users 45 beneficiary were selected by stratified sampling. Secondary data (such as crop data, climate data and other relevant) were taken from different sources. The collected data were analyzed using CROPWAT 8.0 model and GIS software. From the analyses, the result reveled; Average conveyance efficiency was 68.18% and 67% of the main and secondary canals of the scheme respectively. The maximum water loss observed was 0.119 l/s/m on the 175m length canal section of the unlined main canal and 0.159 l/s/m on the 120m length canal section of the left secondary canal. The average storage efficiency in the field was 75.22 % and the average field application efficiency in three field plots were 52.27%. The average deep percolation ratio was 47.73% in the test plots. The losses were deep percolation as the furrows were close ended for upper Dinsira SSI scheme. Technical performance of the irrigation scheme was poor mainly due to illegal water abstraction, sedimentation of canals and inadequate operation and maintenance. The beneficiaries of the scheme (53%) indicated that the Water Users Associations (WUAs) lack clear by-laws and strategies to lead small or major canal operations and maintenances. The majority of canals were covered by weeds, grass and bushes. This was due to weak organizational set up and legal enforcement of bylaws and lack of institutional support. Based on the assessment carried out, we conclude that overall scheme efficiency was under performing (36%). Therefore, to optimize the scheme Dinsira SSI scheme performance, designing of adequate water management approaches are indispensable.