Purpose: This study aimed to explore nurses’ experience in caring for COVID-19 patients. Methods: A total of 10 nurses working in a COVID-19 ward of a public hospital in South Korea were recruited using purposeful sampling. Individual telephone interviews were conducted and then transcribed verbatim. Data were analyzed using qualitative content analysis. Results: Two categories of nurses’ experience in caring for COVID-19 patients emerged; “unstable psychological status” and “adaptation and self-esteem”. “Shortage of staff due to the increase in infected people”, “poor environment due to the urgent construction of a COVID-19 ward”, “unstable operating system”, and “excessive demands and verbal abuse from patients” were “obstacles”, while “cooperation and consideration between colleagues” and “interest and support from the manager” were found to be “sources to boost morale” for nurses in caring for COVID-19 patients. Conclusion This study can be fundamental data for a deeper understanding of the experiences and challenges faced by frontline nurses caring for COVID-19 patients. It is necessary to provide psychological support for nurses and establish a well-structured nursing care system in order to fight a pandemic such as COVID-19.