Introduction: Diabetes mellitus is the most common metabolic disorder. This study, conducted in Arak in 2014, aimed to determine the effects of education, based on a health belief model on the adherence to medication among patients with diabetes. Materials and Methods: For this research, a quasi-experimental study, with a before and after design was used for which 130 patients with diabetes of Arak were selected by sampling method and randomly assigned to two groups (65 cases and 65 controls). The data collection tool used was a questionnaire, the validity and reliability of which had been confirmed. Before the training, the questionnaire was completed for both groups. The intervention group received 4 sessions for one month. Three months after the intervention, both case and control groups completed questionnaires and data were analyzed using the appropriate tests. Results: Three months after the educational intervention, perceived susceptibility, perceived benefits, self-efficacy, internal and external guidelines and performance in the field of medication adherence were all significantly increased with pre-intervention (p<0.05) while the structures, perceived barriers and perceived severity, did not differ significantly to before intervention status (p>0.05). Conclusion: Teaching diabetic patients skills in the context of medication adherence can raise their compliance with medication beneficially affect their health.