Rates of depression are significantly increased in diabetic patients, and even more in the elderly. About 20-30% of patients with diabetes suffer from clinically relevant depressive disorders, 10% of which being affected by the major depression disorder. Moreover, people with depression seem to be more prone to develop an associated diabetes mellitus, and depression can worsen glycemic control in diabetes, with higher risk to develop complications and adverse outcomes, whereas improving depressive symptoms is generally associated with a better glycemic control. Thus, the coexistence of depression and diabetes has a negative impact on both lifestyle and quality of life, with a reduction of physical activity and an increase in the request for medical care and prescriptions, possibly increasing the healthcare costs and the susceptibility to further diseases. These negative aspects are particularly evident in the elderly, with further decrease in the mobility, worsening of disability, frailty, geriatric syndromes and increased mortality. Healthcare providers should be aware of the possible coexistence of depression and diabetes and of the related consequences, to better manage the patients affected by these two pathological conditions.