Grape seed extract (GSE) provides a concentrated source of polyphenols that have antioxidant capacity. An experiment was conducted to investigate the effect of GSE at levels 0.6, 1.8 and 3.6 g kg-1 in broiler chicks (1 to 42 days) on growth performance, relative weights (pancreas, spleen and liver) and lengths (duodenum, jejunum, ileum and ceca) of digestive organs, relative weights of liver fat and abdominal fat, ileal protein digestibility, excreta extractable polyphenol digestibility, and antioxidant activity of diet and excreta. The inclusion of GSE did not affect the performance and the relative liver and pancreas weights. Relative intestinal length was reduced at 21 days of age by the inclusion of GSE. The inclusion of GSE caused an increase of relative spleen weight at 42 days of age. Ileal digestibility of crude protein was increased at 21 days of age in birds fed GSE diets. Excreta extractable polyphenol digestibility was increased at 21 and 42 days of age by the inclusion of GSE in the diets reaching values of 57 to 65 % and 60 to 69%, respectively. Antioxidant activity in GSE diets and excreta exhibited higher scavenging free radical capacity at 21 and 42 days than control diet. We concluded that GSE could be a new source of antioxidant in animal nutrition.