Introduction: Diabetes mellitus is currently one of the most common chronic diseases in the world, which causes various complications. The chronic nature of this disease requires the use of different approaches toward the improvement of adherence to treatment in terms of diet, medications, and related behaviors. Considering the importance of the precise definition of the concepts associated with treatment adherence in diabetes, this study aimed to identify the exact definition, dimensions, barriers, and methods facilitating the improvement of treatment compliance in patients with diabetes mellitus. Treatment adherence is referred to the commitment to carry out drug prescriptions and the implementation of expected health and lifestyle behaviors. The most important barriers to treatment compliance include the weak performance of the treatment team, social constraints, and personal helplessness. Furthermore, the most important strategies to increase treatment adherence are the improvement of patients' knowledge about the disease, test results, and importance of timely control of their complications, as well as the enhancement of the patient's performance and motivation in adherence to the regime treatment by reducing such barriers as fear, satisfaction, support, objective warnings, and inappropriate feedback. Although different dimensions of adherence to treatment are known for the patients, several studies have recommend further investigation of the causes of treatment failure.