In the present study, the in vitro antioxidant potential of aqueous extract of Trapa natans L. fruits rind was investigated. The extract was found to contain a large amount of polyphenols and also exhibited an immense reducing ability. The total content of phenolic, flavonoid and tannin compounds was estimated as 63.81 mg of gallic acid equivalents/g of dry material, 21.34 mg of rutin equivalents/g of dry material and 17.11 mg of total tannin equivalent /g of dry material, respectively. IC50 values for different antioxidant model were calculated as 128.86 microg/mL for DPPH radicals, 97.65 microg/mL for O2*-, 148.32 microg/mL for H2O2 and 123.01 microg/mL for NO, respectively. Reducing power and inhibition of *OH radical-induced BSA oxidation were also determined. The data obtained in the present study suggest that the aqueous extract of Trapa natans L. fruit rind have significant antioxidant activity against free radicals.