Introduction: Type II diabetes, as a chronic disease with various side-effects, can challenge the psychosocial ADAPTATION of patients. This study was conducted with the aim of investigating the effect of an educational program based on Roy’s ADAPTATION model on the psychosocial ADAPTATION of type II diabetic patients in Birjand, Iran in 2013.Methodology: In this quasi-experimental study, 60 patients with type II diabetes, aged 30-70 years, were selected via convenience sampling among patients referred to a diabetes clinic in Birjand. The subjects were assigned to the intervention and control groups via block randomization. First, the demographic form and psychosocial adjustment to illness scale (PAIS) were completed by the two groups. In addition, Roy’s assessment form was completed by the intervention group. The maladaptive behaviors of patients were determined and the program curriculum was designed. Group training was carried out in eight sessions, while face-to-face training was performed in two sessions. The patients were followed-up for one month via phone calls. For data analysis, independent t-test, paired t-test, and covariance analysis were performed, using SPSS version 15.Results: Following the intervention, there was a significant decline in the mean scores of all domains of psychosocial ADAPTATION, i.e., disease perception, vocational environment, domestic environment, family relations, social environment, and psychological distress (P<0.05), with the exception of sexual relationship (P=0.66). In the control group, only the mean score of domestic environment significantly increased after the study, compared to the baseline (P=0.002).Conclusion: The present results indicated the major positive impact of training based on Roy’s ADAPTATION model on type II diabetic patients. In fact, given the changing condition of diabetes, improvement of different aspects of psychosocial ADAPTATION can result in the management of maladaptive behaviors and improvement of patient ADAPTATION. Regarding the cost-effective and non-invasive design of Roy’s ADAPTATION model, it can be incorporated as an effective tool for the analysis of type II diabetic patients.