Abstract: Phytochemicals are extensively found at different levels in many medicinal plants. To investigate the phenolic compound content and in vitro antioxidant activity of hydro-methanolic extract from Prasium majus L. (Lamiaceae). The present investigation comprises, estimation of total polyphenol, flavonoid, tannin, in vitro antioxidant assays such as total antioxidant capacity, DPPH, ABTS, β-carotene and ferric reducing power. P. majus exhibited 64.25 mg GAE g-1 extract of polyphenol phenol content and better scavenging activity of DPPH (IC50 = 7.95 μg mL-1), ABTS●+ (IC50 = 373.78 μg mL-1) and β-carotene (IC50 = 122.56 μg mL-1). Our results clearly demonstrated that hydro-methanolic extract P. majus has antioxidant capacity. Therefore is a valuable source of natural antioxidants.