Antioxidants are vital substances which possess the ability to protect the body from damage caused by free radical induced oxidative stress. A variety of free radical scavenging antioxidants exist within the body which many of them are derived from dietary sources like fruits and vegetables. In the present work, the total phenolic and flavonoid contents of the defatted methanolic extract of Salix tetraspermaRoxb. growing in Egypt and certain fractions (dichloromethane, ethyl acetate, n-butanol and water) derived from it was determined. The ethyl acetate fraction had high phenolic and flavonoid contents (285.48 ± 2.07 mg gallic acid equivalent /g extract and 136.13 ± 2.47 mg rutin equivalent /g extract) respectively. The antioxidant activities of these extracts were evaluated using three tests; 1,1-diphenyl picrylhydrazyl free radical scavenging activity (DPPH) method, total antioxidant capacity (TAC) assay and Azino-bis (3-ethylbenzothiazoline -6-sulfonic acid) (ABTS) assay. The results showed that although all extracts have antioxidant activity but the ethyl acetate fraction is the highest one (SC50= 42.59 ± 0.38 mg/ml for DPPH method; 298.03 ± 6.85 mg ascorbic equivalent/g extract for TAC assay and 925.79± 4.74 mmolTrolox® equivalent / 100 g extract for ABTS assay). The identification of the chemical constituent of the defatted methanolic extract of S. tetrasperma has been performed by HPLC-ESI-MS technique. It was appeared that the chemical constituent of this extract is composed of a mixture of flavonoid and phenolic acid derivatives.