Snake bite is considered as a major occupational health problem in Sri Lanka. A traditional decoction consists of nine medicinal plants clinically proven its efficacy for snake bites. In the present study, an attempt was done to carry out chemical analysis of the decoction. Chemical analyses were carried out for the decoction in terms of (a) phytochemical screening (b) quantification of total phenols and total flavonoids and (c) in vitro antioxidant activities. Present study, revealed the presence of alkaloids, flavonoids, phenols, saponins, steroids and tannins in the decoction. Moreover, total polyphenol and total flavonoid contents of the decoction were 66.03 ± 2.74 mg gallic acid equivalents/g of extract and 18.93 ± 0.90 mg quercetin acid equivalents/g of extract respectively. ORAC value was 3.51 ± 0.23 mg trolox equivalents/g of extract and dose dependent (R2 = 0.9788) DPPH radical scavenging ability was observed. IC50 of the decoction for the DPPH assay was 4.58±0.12 µg/ml. In conclusion, traditional decoction which used to treat snake bites consists of many important phytochemical classes and exhibit potent in vitro antioxidant activity.