Background: Medicinal plants are natural sources of antioxidants effective in the treatment of radical mediated diseases. This study evaluated the in-vitro antioxidant and phytochemical constituents of the methanolic leaves extract of Andrographis paniculata . Methods: Fresh A. paniculata leaves were harvested from a local far m, air -dried and extracted with methanol. Chemical composition, antioxidant activities, and α-amylase enzyme inhibitory potentials of the extract were determined Results: The extract of A. paniculata concentration-dependently scavenges 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2’azinobis (3-ethylbenzothiazoline-6-sulphonic acids) (ABTS) radicals. It scavenges nitric oxide radicals with IC50 of 145.99 μg/ml compared to 167.17 μg/ml of standard ascorbic acid and has 41% activity of standard ascorbic acid ferric reducing power. The extract also inhibited the induction of lipid peroxidation and α-Amylase activity in a concentration-dependent manner. The phytochemical assays employed revealed the presence of various phytochemicals in the extract. Further analysis with gas-chromatography revealed the possible presence of Andrographolide, Deoxyandrographolide, Apigenin, Kaempferol, Quercetin, Methyl vanillate, Methyl Caffeate, Beta-sitosterol, Vanillic acid in the extract. The total phenolics content was found to be 29.11mg GAE/g, and proximate analysis revealed the moisture content, crude protein, crude fat, crude fiber, total ash, and Nitrogen free extract to be 21.89%, 5.66%, 8.74%, 0.95%, 6.87%, and 55.89% respectively. Conclusion: The plant A. paniculata demonstrated good antioxidant potentials and contain various phytochemicals. Therefore, it could be inferred that the effectiveness of A. paniculata as a medicinal plant could be due to the presence of various phenolics and antioxidant compounds in the plant.