Objective: This paper highlighted the effect of selected soil containing metals, viz. Cd, Cr, Cu, Fe, Ni, Pb and Zn on the biochemical compositions and antioxidant activity in leaf of 20 years old two Cassia fistula L. (CF) cultivars. The leaf samples were collected from CF grown on road sides from the states of Maharashtra and Karnataka in India. Methods: Antioxidant activity and total phenol contents from methanolic and aqueous leaf extract were evaluated by assays like oxygen radical absorbance capacities (ORAC), 2, 2 / -Azino-bis (3-ethylbenzothiozoline-6-sulphonic acid) diammonium salt (ABTS) and folin-ciocalteu reagent methods respectively. Maximum dose dependent antioxidant activity was observed in methanol leaf extract of both the cultivars, but marginal variation observed in antioxidant activity. Results: The result revealed that total phenolic content was maximum in the methanolic leaf extract (11.40 ± 0.37 mg g −1 of gallic acid equivalent). A positive correlation between antioxidant activity and total phenol compounds was noticed from both the samples. Furthermore a significant correlation was observed between element contents and antioxidant activities. Conclusion: This was may be due to elements like Fe, Cu, and Zn for accumulation of secondary constituents in the methanolic leaf extract that are major contributors to the antioxidant potential of CF. There were no other heavy metals (Ni, Cd, Pb and Cr) reported in both the samples.