Background and Objective: Human error has been identified as a main cause of most of the major accidents in the world. In order to reduce human errors in the risk assessment and management, it is necessary to assess the risks resulting from human errors which can be guaranteed by conducting human reliability analysis. In the healthcare industry, each year many patients are losing their lives because of clinical errors. Clinical errors, as a global problem, have recently been turned into a challenging issue in various healthcare sector cares. Method: This survey is an analytical-descriptive study, where SHERPA method was used for analyzing human errors in CCU unit of Tehran's Naft hospital. Findings: In total, 450 errors were identified in CCU unit, from which 242 errors (45%) were related to nursing actions, 43 errors (9%) belonged to general practitioners, and 165 errors (37%) were for medical specialists. Also, according to the results of the risk analysis, 12. 45% of errors were unacceptable, 30. 22% had undesirable risk level, 43. 11% were identified with acceptable risk level requiring revision, and 14. 22% had acceptable risk level without a need for revision. Discussion and Conclusion: In the end, it can be concluded that SHERPA method is an appropriate method to be used in the healthcare industry as it is very effective in identifying and analyzing human errors.