Objectives : Diabetes mellitus is the leading cause for vascular complications such as atherosclerosis. The present study is to investigate whether Doinseunggi-tang (DST) improves diabetic vascular dysfunction in type II diabetes. Methods : The db/db mice were treated with high fat/high cholesterol diet and DST (200 mg/kg/day) for 8 weeks. Results : DST significantly lowered blood glucose and systolic blood pressure. In addition, DST also markedly decreased total plasma cholesterol, triglyceride, and LDL-cholesterol, whereas increased the HDL-cholesterol. Vascular relaxation of aortic rings by acetylcholine or SNP was ameliorated by DST in a dose-dependent manner. Damage of vascular intima and hypertrophic of media was improved by DST. Immunohistological study revealed that DST attenuated the increase of ICAM-1, VCAM-1, and ET-1 expression in thoracic aorta. Conclusions : Taken together, DST suppressed hyperglycemia and diabetic vascular dysfunction in type II db/db mice. The present data suggests that Doinseunggi-tang may be prevent a development of diabetic atherosclerosis.