Abstract: Objective: The present study investigated the antioxidant activity of ethanol extract of leaves of Ageratum conyzoides. Methods: leaves of ethanol extract of Ageratum conyzoides were tested for in vitro free radical scavenging assays, nitric oxide, such as hydroxyl radical, inhibition of superoxide anion radical, 2, 2-diphenyl-1-picryl hydrazyl radical (DPPH), and hydroxyl radical. Results: leaves extract effectively scavenged free radicals at all different concentrations and showed its potent antioxidant activity. Further, these effects were in a dose dependent manner. Results were compared to standard antioxidants Conclusion: leaves of Ageratum conyzoides showed strong antioxidant potential.