Introduction: Today, due to the development of technology and automation of industries, the presence of humans in working environments has  decreased. Despite this dramatic decline, the cause of more than 80 percent of the incidents in the oil and gas industry is related to human errors. The purpose of this research was to identify and evaluate the human errors of operators in control rooms working in the Parsian Gas Refinery company.
Method: This cross-sectional study was performed in the control rooms of Parsian Gas Refinery company. A hierarchical task analysis (HTA) was used in the first phase, and then, in the next step in order to the identification and assessment of the human errors, SHERPA method was performed.
Results: Among the total of 218 errors related to the analysis of the SHERPA worksheets, 145 errors (66.5 %) were related to action ones, 61 to (28%) checking errors, 4 (1.8%) to retrieval errors, 6 (2.8%) to communication errors and 2 (0.9%) to selection errors. Also, 41.9% of the errors  caused severe consequences.
Conclusion: It can be concluded that the most prevalent errors are checking and action errors. Appropriate control measures, such as work instructions, staff training as well as employing inspection operators to monitor the performance should be considered as a priority to reduce the occurrence of any identified error or limit their consequences.