Introduction: Effects of whey protein on reduction of blood glucose and appetite have been reported. In the present study the effects of whey protein on glycemic index (GI) and satiety index (SI) of mashed potato were investigated. Materials and Methods: To determine the GI, 10 healthy subjects (6 male, 4 female) were enrolled in the study on 4 separate days at 1 week intervals. On each day, they were given potato puree, potato+5.4 or 9 grams of whey protein or glucose solution in random order. Fasting blood samples were taken at fasting and at 15, 30, 45, 60, 90 and 120 minutes after food ingestion and the GI was calculated. To determine the SI, 20 healthy subjects (10 male, 10 female) were enrolled and on 4 separate days at one week intervals, daily they were given white bread, potato puree, potato+5.4 or 9 grams of whey protein in random order. The satiety was measured at fasting and every 15min over the next 2 hours after food ingestion; using a satiety questionnaire and the SI was calculated. Results: Adding whey protein to mashed potato reduced the area under the blood glucose curve, though it was not significant (p=0.155). No did the GI of potato change significantly (p=0.245). However, the area under the satiety curve of potato increased significantly by adding whey protein (p<0.001); SI of potato was also increased significantly by adding both doses of whey protein (p<0.001). Conclusion: Although adding whey protein did not change the GI of potato, but it significantly increased its SI.