Prevention, or slowing the progression, of diabetic nephropathy is one of the important goals in diabetes care. Although the impact of depression is a concern in patients with diabetes, it is unknown whether there is an association between adherence to hypoglycemic medication and the decline of renal function in comorbid patients with diabetes and depression. This article is a cohort study aimed at examining (1) depression as a predictor of renal function decline, and (2) how adherence to hypoglycemic medication relates to depression and renal function decline in patients with type 2 diabetes.