Background: Logotherapy encourages the individual to find meaning in life, which is recognized as the driving force of every individual in their lifetime. Diabetes, caused by the impairment in metabolism of glucose, fat, and protein, is associated with lack of secretion or dysfunction of insulin. This study aims to investigate the effectiveness of logotherapy on death anxiety, hope, depression, and proper use of glucose control medication in diabetic patients with depression. Methods: The population in the present quasiexperimental pretest–posttest study with control group is comprised of diabetic patients with depression attending Baghban Endocrine Clinic in Sari. A sample of 40 diabetic patients (20 in the trial and 20 in the control group) entered the study. Data were collected using Templer Death Anxiety Scale, Miller Hope Scale, Beck's Depression Inventory, and Medication Adherence Scale. Covariance analysis was used to evaluate the effectiveness of logotherapy on death anxiety, hope, depression, and proper use of glucose control medication, where P value lower than 0.05 is considered significant. Results: Death anxiety and depression of diabetic patients with depression were reduced by following logotherapy training, and their hope was increased. The results confirmed the effectiveness of logotherapy training on death anxiety, hope, and depression in diabetic patients with depression (P < 0.05). Logotherapy was effective on proper use of blood- glucose drugs in depressed diabetic patients and 19% of changes in scores of proper use of medication were caused by the effectiveness of logotherapy (P < 0.05). Conclusions: Logotherapy appears to be a suitable psychological treatment for diabetic patients with depression. [ABSTRACT FROM AUTHOR]