: Type-2 diabetes mellitus is one of the chronic diseases that continues to increase in prevalence, including in Indonesia, with a projection of reaching 10 million sufferers by 2030. The management of diabetes mellitus requires a holistic approach that involves the patient's active role in their self-care. This study aims to analyze the relationship between the role of nurses as educators and the self-care of type-2 diabetes mellitus patients at Royal Prima Hospital Medan. The method used in this study is a quantitative approach with a cross-sectional design. The study population consisted of 522 patients with diabetes mellitus who were registered at the Internal Medicine Poly of Royal Prima Hospital Medan. The sample was 85 respondents, and the purposive sampling technique was used based on the inclusion and exclusion criteria set. Data were collected through questionnaires that measured patients' self-care knowledge and behavior and analyzed using the Chi-Square test to assess the relationship between nurse roles and self-care. The analysis results showed a p-value of 0.001, indicating a significant relationship between the role of nurses as educators and the quality of patient self-care. These findings show that effective education by nurses contributes positively to the understanding and application of self-care by patients. This research is expected to provide deeper insights into the importance of the role of nurses in the management of type-2 diabetes mellitus and provide recommendations to improve the quality of nursing services, and optimize patient care in hospitals.