To examine the relationship between nurses' competency levels in disaster nursing management, their disaster preparedness and disaster preparedness beliefs. Nurses' competency in disaster nursing management makes disaster response easier. Factors that may affect this reason should be examined. The study was conducted between April and July 2023 with nurses working in a province in the first-degree earthquake zone in Turkey. The sample of the study consisted of a total of 207 nurses who were selected from primary, secondary, and tertiary care institutions by using the stratified sampling method. Data were collected with a personal information form, the Competencies for Disaster Nursing Management Questionnaire, the Disaster Preparedness Scale, and the General Disaster Preparedness Beliefs Scale. Mann-Whitney U and Kruskal-Wallis tests, Spearman regression coefficient, and multiple linear regression analysis were used to analyze the data. There was a positive correlation between nurses' competency levels regarding duties and responsibilities and their disaster preparedness levels. Having disaster-related training also positively affected the level of competence in duties and responsibilities. Belief in disaster preparedness and having "partial" knowledge about the disaster had no relationship with competencies. According to the International Council of Nurses and current studies on disaster nursing, "competence areas" are among the priority study subjects. According to the study results, disaster preparedness and having disaster-related education are effective factors in nurses' competencies related to duties and responsibilities. The results of this study may increase awareness in the healthcare system about nurses' disaster management competency levels and the factors that may affect this. It is recommended that disaster preparedness and disaster-related education factors should be taken into account in the initiatives and policies to be planned to improve the duty and responsibility competence of nurses.