OBJECTIVE: The purpose of this study was to evaluate the antioxidant activity, phenolic and flavonoids contents of selected medicinal plants form the Western region of Nepal.METHODS: The antioxidant activity of selected medicinal plants were determined by using 2, 2-diphenyl-1-picrylhydrazyl radical scavenging activity; total ferric ion reducing ability through spectroscopic analysis. The content of total phenols was determined using Folin-Ciocalteu reagent, whereas Aluminum chloride colorimetric method was used for flavonoid determination.RESULTS: Extracts of Syzygium Operculatus(87%),Astilbe Rivularis(83%) and Mallotus Philippnensis(88%) showed significant free radical scavenging activity with effective concentration(EC50) close to that of ascorbic acid. Syzygium Operculatus(96%),Astilbe Rivularis(97%) and Mallotus Philippnensis(97%) had potent reducing power in concentration dependent fashion. Those plant extract with higher free radical scavenging and ferric reducing effect also showed the greater content of both phenols and flavonoids, suggesting the correlation between polyphenolic content and antioxidant activity. Those plant extracts which showed better antioxidant activity assays, also demonstrated higher total phenol and flavonoid contents. These three plants showed the presence of higher amount of phenols and flavonoids.CONCLUSION: This study may provide the scientific basis for the traditional use of those plants and may provide valuable idea for further research.