Introduction: Diabetes is one of the main pandemics in recent years. Its association with depression increases the risk of mortality and morbidity. The coexistence of both diseases leads to poor management of diabetes, which leads to a worse quality of life. Objective: To determine the frequency of depression in patients with diabetes mellitus and the effect of both pathologies on the quality of life in patients who attend outpatient appointments at public health facilities in Lima and Callao. Methodology: Secondary analysis of the Epidemiological Study of Mental Health of depression in diabetic adults. The instrument used to determine the depressive episode was the MINI (Mini-International Neuropsychiatric Interview) while quality of life was measured using the Mezzich Quality of Life Index. Diagnosis information of type 1 or 2 diabetes was obtained from the daily medical record (HIS) of care. Results: The frequency of depression in the 471 patients with diabetes was 5.8% in the last two weeks. While the annual frequency was 8.6% and 31.8% at some point in life. Being a woman was associated with a greater frequency of depression. Quality of life was lower in patients with diabetes and depression (p < 0.005). Conclusions: The frequency of depression in patients with diabetes who are treated on an outpatient basis in public health centres is higher than the general population and their quality of life is significantly reduced, which raises the need for considering depression as an additional factor to the burden of morbidity of this condition.