Purpose: The main purpose of this study was to investigate the direct and indirect effects of psychosocial factors on self-care behavior and glycemic control in Turkish patients with type 2 diabetes mellitus. Method: The study used a cross-sectional questionnaire survey design (N = 350). Data were collected using the Summary of Diabetes Self-Care Activities Scale and the Multidimensional Diabetes Questionnaire. The relationship between the study variables was analyzed using Pearson's correlation coefficient and structural equation modeling. Results: Self-efficacy was associated with social support, outcome expectancies, perceived interference, educational level, and self-care and A1C. According to the structural equation model, self-efficacy was the predictor variable that influenced both self-care and glycemic control. Conclusions: Self-efficacy in achieving desired health outcomes was found to play a central role in Turkish patients. Although interventions are planned and implemented to achieve and maintain self-management in individuals with diabetes, strengthening psychosocial factors, particularly self-efficacy, may contribute to adjustment to disease and good glycemic control in the long term.