Thalictrum foliolosum is an endemic herb of the temperate Himalayas and eastern China. These plants have been used for past several decades by indigenous people to treatment of fever, gastrointestinal disease, intestinal obstruction, jaundice and eyesight problems. Although a wide diversity of alkaloids and polyphenolic compounds are found in various Thalictrum species, the presence of major polyphenolic compounds in the T. foliolosum has not been much studied. In present study, both wild-collected (WC) and in vitro propagated (IVP) plants materials such as leaves and roots were used for polyphenolic compounds identification and quantification as well as different antioxidant assay. For quantitative analysis of polyphenolic compounds, extracted plant materials were subjected to HPLC–PDA. Additionally, 2, 2–diphenyl–β–picrylhydrazyl (DPPH) free radical and reducing power assay (RPA) were used to determine the antioxidant activity of various extracts. Results showed 12–13 polyphenolics compounds were identified in roots and leaves of WC and IVP plants. Spectrophotometric and HPLC analysis revealed that IVP roots had higher content of phenolics (TPC) (1489.80 ± 9.15 µg GAE/g) and flavonoid content (TFC) (783.58 ± 8.23 µg RE/g). However, strong antioxidant potential was found in chloroform fraction of IVP roots (DPPH IC₅₀ −23.36 ± 0.60 µg/ml). Also, a positive correlation was existed between the antioxidant activity and phenolic and flavonoid content. Presence of various phenolic compounds along with the previously described alkaloids makes this Thalictrum species therapeutically important. The enrichment of polyphenolic compounds in micropropagated T. foliolosum plants provides the alternative option for various pharmaceutical industries as well as conservation.