Introduction and Purposes: Nurses play important roles in terms of health care. Clinical competency is one of the significant merits of nursing and its evaluation can lead to recognition of fields requiring improvement. Hence, the present study was conducted with the purpose of self-evaluation of nurses' clinical competency based on Benner theory. Implementation Method: This study is sectional descriptive. By census method, the clinical competency of 83 nurses was reviewed as self-evaluation in 9 different wards of a selective hospital in Abadan City. The entrance criteria was to have at least 6-month's experience and satisfaction with participating in the study. The means to gather data was a questionnaire which investigated 73 skills in 7 various fieldss. For each skill, the nurse at first gave themself a score from 0 to 100, and then, he/she determined the use rate of that skill using a four rating Likert scale. The data, descriptive and inferential statistics were analyzed by SPSS software. Results: The average of total score of nurses' clinical competency was about 82/98 11/72 percent. Overall, the maximum total average was 86/71 11/26 related to field of management conditions and the least total average belonged to 78/33 15/29 related to field of quality assurance. Moreover, the results showed that nurses use 94/5 percent of practical skills related to management conditions occasionally and frequently and this rate is much more in comparison to other fields and indicates more use of skills about which nurses have more qualification. Discussion and Conclusions: The results demonstrated that totally the level of clinical competency and use of nursing skills are desirable in the studied population. By the results of such research, the skills needing more training can be recognized and holding re-education courses can help to not only improve these skills, but also to develop the nursing clinical competency and patients' satisfaction as a whole.