The Covid-19 pandemic has caused nurses to experience various physical and mental pressures to deal with case escalation. The workload of nurses is increasing, and they are required to quickly adapt to various changes. High self-efficacy is needed for motivation and performance as well as controlling stress. This study aims to obtain an overview of the sources of nurse self-efficacy and explore other themes related to nurses' self-efficacy in the Covid-19 Isolation Room. This research is qualitative research conducting semi-structured in-depth interviews with 12 informants. The informants were selected by purposive sampling consisting of the shift nurse, the team leader, and the head nurse. Data analysis techniques with manual thematic analysis. The stress faced by nurses in the Covid-19 Isolation Room is related to workload, job risks, and relational relationships at work and in the community. Sources of informants' self-efficacy were obtained from mastery experiences through internships, vicarious experiences from role models, and social persuasion from friends and superiors. Three themes were found that affect selfefficacy, namely personal, organizational, and external variables with several subthemes. Personal variables such as altruism, commitment, self-motivation, and spirituality are dominant and fundamental in shaping self-efficacy which is accelerated by organizational variables and supported by external variables. In order to increase nurses' self-efficacy, it is necessary to utilize self-efficacy sources, maximize personal variables and get support from family and organizations.