Introduction: To err is human but the delivery of healthcare is an enormous responsibility and detection and measurement of medical events is the main component of patient safety. Root cause analysis (RCA) is one of the very useful tools that facilitates the environment in order to get people ideas and is beyond involving a person or individuals. The present study aims the root cause analysis of an adverse event in one of the hospitals in Iran.

Methods: This study is a qualitative survey and the main steps of it are as follows: defining event, team formation, data collection using deferent methods (brainstorming, interview, documents reviewing, analysis of changes, nominal group and fish bone diagram), identifying the root factors and causes and ultimately providing and offering the solutions.

Findings: The seven root causes of this event were as: cluttered treatment room, taking the patient’s IV line in sitting position, patient reception in addition to the beds approved, the limited space of the treatment room, the maximum elapsed time of nurse in documentation, placing the patient alone in the treatment room and rapid preparation of the patient. Then, suggestions for removal of any of the root causes were presented.

Conclusion: Change of system approaches, organizational changes and the establishment of standards in each system is one of the most important issues in prevention of the future events. All of the hospital authorities and managers must use the approach of RCA in risk management in their organization as each system may have some underlying problems that aren’t found in other systems.