In order to secure and sustain food security in Ethiopia the government is undergoing large- and small-scale schemes all over the country. However, some of the schemes are working under desired performance. Hence Irrigation scheme performance assessment is vital to evaluate the impacts of irrigation practices, to identify performance gaps and to improve system performances. Therefore, the research was carried out to evaluate the application efficiency, conveyance efficiency, water use performance, water delivery, on-farm water management and organizational performances of Geray rehabilitation small scale irrigation scheme. The irrigation scheme command area was 600 ha and during the study season, the irrigated area was 570ha. CROPWAT 8.0 model and GIS software were used to analyze the data. Collecting primary and secondary data of the irrigation scheme has been carried out by the study. Primary data collection included canal water flow measurement, soil moisture before irrigation and after irrigation, depth of water applied to the field, field observation and interviewing beneficiary farmers. Secondary data were collected from secondary sources that were Woreda Agriculture Office and WUA of the scheme. In order to evaluate the irrigation water, use efficiency of farmers at field level three farmers were selected from each irrigation projects in relation to their location (from the head, middle and tail end water users). To assess and evaluate on farm management practices and institutional supports services of the scheme, well-organized questionnaires were developed and interviewed. The results obtained showed that the main canal conveyance efficiency was 96%, the average conveyance efficiency of the tertiary canals was 63%. The main canal efficiency was in the acceptable range. However, the conveyance efficiency of the tertiary canals was found below expected standards. The Application efficiency result on three farmers’ farm located on the head, middle and tail of the command were found 43.32%, 41.56%, and 46.26% respectively. The overall efficiency of the irrigation scheme was 34.8%. The relative water supply and the relative irrigation water supply were 4.2 and 4.8 respectively. Almost 52% of respondents observed significance structural failure due to poor operation especially in tertiary canals reflecting that the maintenance condition of irrigation infrastructures was bad. From the results it was understood that that the amount of water supplied was sufficient for the water demand of the scheme. The overall services given by WUA and other relevant institutions in terms of managing the scheme and supporting beneficiaries were poor. The overall performance of the scheme is low. Therefore, proper irrigation management system, adequate operation and maintenance of the system and strong WUA should be required to xv improve the irrigation scheme performance and to ensure the sustainability of the irrigation scheme.