The present study was aimed out to evaluate the antioxidant and free radical scavenging activity of methanolic extract of Plumeria acuminata leaves (Apocynaceae) in various systems. DPPH radical, superoxide anion radical, nitric oxide radical and hydroxyl radical scavenging assays were carried out to evaluate the antioxidant potential of the extract. The antioxidant activity of methanolic extract increased in a dose dependent manner. About 50, 100, 200, 300, 400 and 500 μg of Methanol Extract of Plumeria acuminata (MEPA) showed 46.01, 52.83, 57.43, 61.38, 68.27 and 73.14% inhibition, respectively on peroxidation of linoleic acid emulsion. Like antioxidant activity, the effect of MEPA on reducing power increases in a dose dependent manner. In DPPH radical and nitric oxide radical scavenging assays, MEPA exhibited maximum activity of 60.42 and 56.38% inhibition at the concentration of 125 μg mLG-1. Moreover, the MEPA was found to scavenge the superoxide generated by PMS/NADH-NBT system. MEPA was also found to inhibit the hydroxyl radical generated by Fenton`s reaction, where the IC50 value of MEPA was found to be 74.39 μg mLG-1 and for catechin the IC50 value was found to be 5.27 μg mLG-1, which indicates the prooxidant activity of MEPA. The amounts of total phenolic compounds were also determined in this study. The results obtained in the present study indicate that the MEPA can be a potential source of natural antioxidant.