In diabetic kidney disease, detection of urinary albumin is recommended to aid in diagnosis, evaluate disease severity, and determine effects of therapy. However, because typical histopathologic changes in diabetic kidney disease or early progressive renal decline may occur in patients with normoalbuminuria, urinary albumin may not be sufficient to identify patients with early-stage diabetic kidney disease or to predict its progression. Therefore, intensive efforts have been made to identify novel noninvasive urinary biomarkers to discriminate patients with a higher risk of end-stage renal failure. Because diabetic kidney disease progression is associated with the extent of histologic changes in the glomeruli and the degree of tubulointerstitial changes, urinary biomarkers that accurately reflect the degree of histopathologic damage may be excellent biomarkers. This review article summarizes the clinical significance of new urinary biomarkers in the early detection of diabetic kidney disease.