Purpose : This study aimed to understand and describe the nurses’ experiences caring for severe COVID-19 patients at isolation room with negative pressure in South Korea.Methods : Data were collected through individual in-depth interviews from February 16 to March 31, 2021 with 11 nurses who had been caring for severe COVID-19 patients at isolation room. Verbatim transcripts were analyzed according to Colaizzi’s phenomenological analysis.Results : As a result, 5 theme clusters were extracted about nurses’ experiences. The 5 theme clusters, “Adapting to unexpected adversity”, “Accepting unresonable and heavy work”, “Dulness and disconnection from the outside world”, “Changing in perception of new infectious diseases”, and “Pathetic isolated patients” emerged.Conclusion : The results of this study provided a deeper understanding of nurses struggling to care for COVID-19 severe patients. This study is expected to be useful in providing basic evidence for improving intensive care practices and for preparing policies in other infection disease situations.