The present study is designed to extract and investigate the bioactive phytoconstituents, their secondary metabolites, and antioxidant potential from the leaf extracts of Clematis napaulensis belonging to the family Ranunculaceae. Extract was investigated for its preliminary phytoconstituents by chemical analysis method. Quantification of total phenolic content by Folin-Ciocalteau assay; Total Flavonoid Content and Total Triterpenoid Content (TTC) were quantified by colorimetric method. Antioxidant potential was evaluated in vitro using Phosphomolybdenum assay, Hydroxyl radical scavenging activity, Reducing power assay, and the DPPH method. The preliminary phytochemical screening results suggested that a wide variety of pharmacologically active phytoconstituents such as phenolic compounds, alkaloids, glycosides, flavonoids, saponins, tannins, triterpenoids, gums, proteins, and reducing sugars were present whereas non-reducing sugar was absent. The total phenolic content in the methanolic extract was 0.8308 μg/mL of gallic acid equivalent; the total flavonoid content of the plant was 1.3850 μg/mL of quercetin equivalent and the total triterpenoid content was found to be 1.414 μg/mL of oleanolic acid equivalent. In vitro antioxidant studies revealed that Clematis napaulensis possess good antioxidant potential. This is the first report of Clematis napaulensis, the phytochemical screening results suggested that the extract would be a potential alternative also it can be explored to discover and development of new chemical moieties for treating various diseases.