OBJECTIVE: To examine the impact of a self-care program designed using Peplau's theory on adherence and self-care in elderly diabetic patients. METHODS: This semi-experimental study involved 102 elderly diabetic patients from a diabetes clinic in Hormoz, Iran, in 2023. Partici-pants were randomly allocated to either the control group (n=51) or the intervention group (n=51). Before and two weeks after the intervention, participants completed a demographic information questionnaire, the Modanloo Adherence to Treatment Questionnaire for Patients with Chronic Illness, and the Summary of Diabetes Self-Care Activities Scale. The intervention group received a self-care educational program based on Peplau's therapeutic communication theory, delivered in three phases: orientation, working, and termination. The program focused on key diabetes self-care factors including diet, medica-tion adherence, physical activity, blood sugar monitoring, and foot care. Educational sessions were conducted in small groups or individually in the clinic's education room. The control group received routine educational content provided by the diabetes clinic. RESULTS: The findings showed that the difference between the pre-post mean scores was significantly higher in the intervention group compared with the control group in the total self-care score, as well as in its dimensions: diet, blood sugar regulation, and foot care (p<
0.002). On the other hand, in terms of adherence, no significant difference was observed in the mean difference between groups for the total score (p=0.307), although a statistical difference was found in the dimensions of willingness to participate in treatment (p=0.035) and ability to adapt (p<
0.002). CONCLUSION: The self-care educational program based on Peplau's theory improved the self-care and two dimensions of the adherence: willingness to participate in treatment and ability to adapt in diabetic patients.