The objective of the study was to assess the organizational capacity of Oromia Water Works Design and Supervision Enterprise. A mixed research design was applied to conduct the study. Both probability and non-probability sampling techniques were used to select respondents. systematic sampling was used to select respondents to survey and non-probability (purposive) sampling was used to select key informants. Data were gathered from both primary and secondary sources by employing survey and key informant interview and document review. SPSS was used for analyzing quantitative data and descriptive statistics such as frequencies percentages and mean are used describe the data, results were presented textually, in tables and using graph. Data generated from key informants and document reviews, described verbally. The findings indicated that Oromia Water Works Design and Supervision Enterprise had well designed organizational structure. However, functional units are not adequately decentralized; there was also a gap in designing organizational structure on scientific and its necessity for work. The leadership was also found to be competent & well qualified. There wasn’t well organized performance measurement, monitoring system and tools to monitor its staff. Human resource evaluation was not conducted timely and working environment is not conducive for employees. Based on these major findings only about 22.54% is indicated the strength of sub factors under Organizational structure & Working Environment & The rest 65 sub factors which shared about 77.5% of the total value revealed that the over all organization Capacity of OWWDSE is not well organized & has a capacity gaps to deliver its mission of establishment. So ,it could be safely concluded that OWWDSE was moderately effective in discharging its organizational activities on some aspects of capacity assessment components. Regarding budget control and evaluation system; timely purchase of goods and services; collection of revenue generated on time; forecasting future monetary needs and requirement; having transparent and verified financial resources rules are areas of weaknesses of OWWDSE. Finally, Revising organizational structure for decentralization of functional units, reviewing internal and external factors, measuring performances and taking corrective actions timely, strengthen decision making practice, efficient use of human resources, making working environment attractive, due attention on organizing, storing and using different data and documents and focusing on it’s important capacity assessment components limitations for farther success of the organization are among forwarded recommendations based on conclusions drawn.rnKey words: Leadership Capacity, Organizational Capacity Assessment, Oromia Water Works Design and Supervision Enterprise