The purpose of this study was to investigate the polyphenol-rich cornelian cherry (Cornus mas L.) and barberry (Berberis vulgaris) fruits extract on reducing the in vitro starch digestibility of white bread and evaluation of glycemic indexes. Generally, all berry fruit types reduced the starch digestibility and predicted glycemic index of white bread. When we evaluated the association between the RDS and HI, the amount of RDS was decreased by the treatments of barberry extract and cornelian cherry extract and the HI of white bread was also decreased. It is thought that the barberry has more inhibitory effects on α-amylase activity than cornelian cherry. We also demonstrated that dietary polyphenols such as anthocyanins and catechins found in cornelian cherry and barberry fruit reduced starch digestion by inhibiting α-amylase and α-glucosidase.