The present research account is an investigation on the phytochemical content, antioxidant property and antibacterial activity of the whole plant crude extract of Parthenium hysterophorus. Plant extract were prepared in ethanol solvent. Phytochemical screening showed the presence of different bio-constituents such as Alkaloids, Phenols, Flavonoids, Steroids, Cardiac Glycosides and Carbohydrates was detected in ethanol solvent extract. Free radical scavenging assay against the 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) proved the strong antioxidant property of the plant. A highest of 89.23±5.40 free radical inhibition was achieved with ethanol extract and the value was very close to that obtained with ascorbic acid standard (98.23 ± 5.4). The ethanol extract of whole plant was found to be exhibit staphylococcus aureus, bacillus cereus, salmonella typhi, and klebsiella. The extract and fractionates of fresh leaves of Parthenium hysterophorus showed a significant and remarkable activity against all the microorganisms. The findings of the present study provided a strong scientific background for recognizing this plant as potential medicinal herb used by many local tribes of South India.