To investigate the effects of Hachimi-jio-gan on diabetic nephropathy, we employed an animal model, rats subjected to sub-total nephrectomy followed by streptozotocin injection, and administered Hachimi-jio-gan orally at a dose of 50, 100 or 200 mg/kg body weight/day for 15 weeks. The administration of Hachimi-jio-gan reduced dose-dependently the elevated blood glucose and urinary protein excretion levels in rats with diabetic nephropathy over the experimental period, whereas it increased creatinine clearance significantly, suggesting that Hachimi-jio-gan would prevent or delay the progression of diabetic nephropathy. In addition, the serum glycosylated protein and urea nitrogen levels were markedly elevated in rats with diabetic nephropathy compared with normal rats, and were significantly reduced by the administration of Hachimi-jio-gan, whereas Hachimi-jio-gan reversed the decrease in the serum albumin level. The serum triglyceride and total cholesterol concentrations were reduced by Hachimi-jio-gan, implying that Hachimi-jio-gan would improve the metabolic disorder of lipids caused by diabetic nephropathy. Moreover, Hachimi-jio-gan inhibited lipid peroxidation in the serum and kidney, which suggests that Hachimi-jio-gan would ameliorate oxidative stress associated with diabetic nephropathy. Furthermore, the disorders of the glucose-dependent metabolic pathway due to this pathological condition were also normalized by the administration of Hachimi-jio-gan through decreases in advanced glycation end-product formation and sorbitol levels in the kidney. Hachimi-jio-gan protected against the development of renal lesions, glomerular sclerosis, tubulointerstitial lesions, mesangial matrix expansion and arteriolar sclerosis, estimated by histopathological evaluation and scoring. This study suggests that Hachimi-jio-gan may be a novel therapeutic approach to improving diabetic nephropathy.