The antidiabetic activity of the total lignan from the plant Fructus Arctii, used in China for the control of diabetes, was investigated in models of alloxan‐induced diabetic mice and hyperglycemic‐hyperlipidemic diabetic rats. The biochemical parameters studied were: blood glucose, glucose tolerance, serum insulin, serum triglycerides, total cholesterol and high density lipoprotein (HDL). Total lignan was given to mice and rats daily for 10 days at doses of 2.0, 1.0, 0.5 g/kg and 1.38, 0.69, 0.35 g/kg respectively. The alloxan‐diabetic animals showed significant reductions in plasma glucose, triglycerides and total cholesterol after treatment with the total lignan from the plant Fructus Arctii and glibenclamide (used as standard) compared with the diabetic controls, while the glucose tolerance, serum insulin level and HDL‐cholesterol were elevated without the risk of hypoglycemia. In conclusion, the total lignan from the plant Fructus Arctii has been proven to be a safer antidiabetic agent and might help to prevent diabetic complications. It can serve as a good adjuvant in the present armamentarium of antidiabetic drugs. Copyright © 2007 John Wiley & Sons, Ltd.