Background: Certain factors may facilitate or inhibit the formation of moral sensitivity in nurses performing cardiopulmonary resuscitation (CPR). The identification of these factors in the context can help develop strategies to promote nurses’ moral sensitivity and offer new insights into the consequences of their moral decisions. Objective: Taking into account the possibly multi-factorial nature of moral sensitivity, this study aimed to identify the factors affecting the formation of nurses’ moral sensitivity in CPR settings. Research design and methods: This study performed (...) a conventional qualitative content analysis. Twenty-one participants were selected via purposive and theoretical sampling. The data were collected through in-depth semi-structured interviews and simultaneously analyzed via content analysis. Participants and research context: In total, twenty-one participants (fourteen clinical care nurses, three head nurses, two educational supervisors, and two faculty members) from different cities of Iran were interviewed. Ethical considerations: The research was approved by the Ethics Committee of Urmia University of Medical Sciences in Iran (IR.UMSU.REC.1399.337). Findings: Four categories (underlying factors, professional factors, organizational inhibitors of ethics, and professional limitations) and 13 sub-categories were extracted. Discussion: The formation of moral sensitivity requires a range of ethical standards and their maintenance, not only at the individual level but also at the profession, organization, and community levels. So eliminating inhibitors of ethics in these contexts can improve nurse’s ethical performance in CPR settings. Conclusion: Any measures taken or decisions made by nurses in CPR are driven by numerous ethical issues to which nurses must be morally sensitive. Some factors facilitate and some inhibit the formation of moral sensitivity in nurses. (shrink)