Introduction: Diabetes mellitus is one of the most expensive chronic illnesses for both patients and governments, which faces the patients with a lot of problems.  The chronic nature of diabetes affects the patient's physical, psychological, personal, and interpersonal performance, as well as psychological well-being. As a result, this disease is regarded as a stressor for the patients. There are different managerial theories to improve the health status of diabetic patients, one of which is Pender model. Regarding this, the present study was performed to determine the impacts of an educational program based on Pender model on the psychological well-being of type II diabetic patients.

Materials and Methods: This clinical trial was conducted on 72 patients with type II diabetes mellitus referring to Hazrat Sedighe Tahere Diabetes Center. The study population was selected through simple random sampling method, and then assigned into two groups of control (n=36) and intervention (n=36). The Reef psychological well-being scale was filled out by both groups under the researcher’s supervision. The data were analyzed by independent t-test, Q-square, Man Whitney U test, and ANOVA in SPSS software (version 18).

Results: According to the results, the control group showed no significant difference in the psychological well-being mean score before, immediately after, and one month after the intervention (P>0.05). However, this difference was statistically significant in the intervention group (P<0.05). There was a significant difference between the intervention and control groups in terms of psychological well-being mean score at the three stages of the intervention (P<0.05). The results of the LSD test revealed that the intervention group had a significantly higher psychological well-being mean score before the intervention, compared to immediately after (P=0.004) and one month after the intervention (P=0.007).

Conclusion: Given the effect of Pender model-based educational program on the psychological well-being of the type II diabetic patients, it is recommended to apply this method as an effective, useful, and cost-efficient approach.