Aim To explore and understand moral distress from the perspective of and as experienced by critical care nurses in Korea. Background The concept of moral distress among critical care nurses must be more broadly explored using a qualitative approach. Design Giorgi's phenomenological research approach was used. Methods A purposive sampling was used to select 14 critical care nurses. In‐depth face‐to‐face interviews were performed in Korea from March 2012–December 2013. Findings Five main themes of moral distress emerged: (1) ambivalence towards treatment and care (notably prioritizing work tasks over human dignity, unnecessary medical treatments and the compulsory application of restraints); (2) suffering resulting from a lack of ethical sensitivity; (3) dilemmas resulting from nurses' limited autonomy in treatments; (4) conflicts with physicians; and (5) conflicts with institutional policy. Conclusion Staff shortages are aggravated by high staff turnover caused by ethical suffering. The resulting lack of staff can, in turn, give rise to added ethical conflicts as part of a vicious circle, leading to decreased patient satisfaction.