Depressive symptoms are common among patients with diabetes and may have a significant impact on self-management and health outcomes. In this study we predicted that: 1) there would be a significant association between depressive symptoms and diabetes symptom burden, physical functioning, diabetes self-care, and HbA1c levels; and, 2) that the association between depressive symptoms and HbA1c levels would be significantly greater in type 1, as compared to type 2 diabetic patients. This cross-sectional observational study of 276 type 1 and 199 type 2 diabetes patients took place in a tertiary care specialty clinic. We collected self-reported data on depressive symptoms, complications, medical comorbidity, diabetes symptoms, diabetes self-care behaviors, physical functioning, and demographics. From automated data we determined mean HbA1c levels over the prior year. We performed linear regression analyses to assess the association between depressive symptoms and diabetes symptom perception, diabetes self-care behaviors, physical functioning, and glycemic control. Among patients with type 1 and 2 diabetes, depressive symptoms were associated with greater diabetes symptom reporting, poorer physical functioning, and less adherence to exercise regimens and diet. There was a significant association between depressive symptoms and HbA1c levels in type 1, but not type 2 diabetic patients. Because of their association with clinical aspects of diabetes care such as diabetes symptom reporting and adherence to diabetes self-care, depressive symptoms are important to recognize in treating patients with diabetes.