Type 2 diabetes mellitus relavant to insulin resistance is a chronic and hard to control. In order to develop an antidiabetic agent from natural products, anti-hyperglycemic effect of herbal formula containing Mori Follium, Euonymi Lignum Suberalatum and Ginseng Radix(MEG) was investigated in db/db mice. Treatment group was administered orally with MEG formula at a dose of 300 mg/kg for 5 weeks, and blood glucose, insulin and lipid levels were determined. MEG treatment group showed a marked decrease in fasting blood glucose level and insulin resistance index(IRI) compared to those in diabetic control. Improvement of insulin resistance(60.6%) was indicative of reducing lipid levels in plasma and triglyceride contents in muscle and adipose tissue. In addition, expressions of an insulin responsive gene, glucose transporter 4(Glut4), in muscle and adipose tissue were upregulated in MEG treatment group. Compared islet morphology between groups, MEG formula prevented the ${eta}$-cell destruction caused by high blood glucose. Taken together, MEG formula can act as an anti-hyperglycemic agent with insulin sensitizing effect, and thus deserves a clinical trial in the future.