The core competencies in disaster nursing, nurses' roles in disaster management and the potential barriers are assessed with a view to developing disaster nursing in Slovenia. Despite training and experience, many indicators show nurses are deficient in skills involving emergency and disaster-preparedness competencies. Nurses report little familiarity with disaster-planning skills, the implementation of disaster guidelines and assessment of patients subject to a disaster circumstance. A cross-sectional descriptive study was conducted based on data collected through an online survey. 118 registered nurses from different clinical settings in Slovenia participated in the study. Data were collected according to the Slovenian version of the Disaster Nursing Core Competencies Scale (Sl-DNCC-Scale). The scale was limited to a 7-point Likert response format (from 1 = strongly disagree to 7 = strongly agree). The results show the registered nurses perceive the core competencies of disaster nursing to be important to their preparedness for disaster situations (median = 161; range 74-189). Registered nurses who work in nursing homes and nurse managers are more aware of the importance of acquiring the listed competencies for unexpected events (p = 0.011 and 0.060 respectively) and the importance of their active role in disaster management (p = 0.027 and p = 0.004, respectively). To effectively deal with a disaster, nurses must be well prepared for unexpected events and more actively involved in disaster management. This study demonstrates that nurses regard the core disaster nursing competencies as important and greatly needed in various healthcare facilities. Future studies in this area should focus on ways to implement these competencies in nursing education.