Background: The COVID-19 pandemic has put heavy pressure on nurses. Psychiatric nurses are also exposed to moral distress due to the special conditions of psychiatric patients and patient's lack of cooperation in observing health protocols. This study has been conducted to explore and describe factors that caused moral distress in Iranian psychiatric nurses during the COVID-19 pandemic.

Method: This qualitative study with a conventional content analysis approach involved 12 nurses at the Shiraz University of Medical Sciences in Iran. This study was conducted in the winter of 2021. Data collection was performed by semi-structured interviews, data analysis was performed based on the five steps of Graneheim and Lundman.

Results: By continuous comparison and integration of data, 17 subcategories, 8 subcategories, and 3 categories were extracted from 252 initial codes. The causes of moral distress in psychiatric nurses during the COVID-19 pandemic were identified as emotional responses (Fear and Doubt), relational factors (Nurses' Relationship with Each Other, Nurse-physician Relationship, and Relationship whit Patients), and Institutional factors (Lack of Attention to Health Instructions, Failure to complete the treatment process for patients and Institutional Policies).

Conclusion: New dimensions of the causes of moral distress associated with the COVID- 19 pandemic are discovered in this study. Managers and planners should equip psychiatric hospitals with isolation facilities and Personal Protection Equipment for patients and nurses. Strengthening the ethical climate by improving communication skills and individual nursing empowerment to prevent moral distress is recommended.