Background: Korean red ginseng is one of the most popular herbs worldwide due to the belief that it contains ingredients that possess a variety of health enhancing effects including anti-diabetic effects. The objective of this study was to determine whether Korean red ginseng supplement has an effect on insulin sensitivity in healthy overweight or obese adults without overt diabetes and hypertension. Methods: In a double-blinded, placebocontrolled, randomized trial, a total of 68 participants (BMI ≥23 kg/m^2) received either 6 g of Korean red ginseng rootlets (n=34) or a placebo each day over a 12 week period. Results: Similar insulin levels and insulin sensitivity index were observed at baseline in the Korean red ginseng and control groups. Korean red ginseng had no significant effect on improving the insulin sensitivity over time. Korean red ginseng does not improve the insulin sensitivity of overweight and obese subjects who do not have diabetes or hypertension.