The present study investigate the qualitative and quantitative analysis of the major bioactive constituents of 13 medicinally important plants, namely Woodfordia fruiticosa, Adhatoda vasica, Chenopodium ambrosoides, Viburnum cotinifolium, Euphorbia hirta, Vitex negundo,Peganum harmala, Broussonetia papyrifera, Taraxacum officinale, Urtica dioica, Verbascum thapsus, Caryopteris grata and Mimosa rubicaulis collected from different localities of Margalla Hills, Islamabad Pakistan, for their authentication. Alkaloids, saponins, tannins, anthraquinones, flavonoids, flavons, flavonols and chalcones, terpenoids, phlobatanins, coumarins, steroids and cardiac glycosoides were analyzed qualitatively where as alkaloids, flavonoids, tannins, phenols and saponins were analysed quantitatively too. In W. fruticosa andV. cotinifolium, all the constituents were detected except coumarins and steroids. All the constituents were detected in A. vasica, C. ambrosoides and P. harmala except anthraquinones, coumarins, steroids and terpenoids. V. negundo exhibited all the studied phytochemicals except coumarins, steroids and phlobatanins. Maximum alkaloid content (1.13%) was recorded in A. vasica followed by P. harmala (1.11%), W. fruticosa (1.036%) andV. cotinifolium (0.90%). Maximum (0.87%) phenolic content was observed in methanolic extract of W. fruticosa. Tannin content was recorded maximum (15.75%) in M. rubicaulisfollowed by W. fruticosa (14.16%), C. grata (13.4%), V. cotinifolium (12.33%), E. hirta (11.2%),B. papyrifera (10.56%) and P. harmala (10.2%). Maximum flavonoid content (10.95%) was observed in V. negundo. Maximum saponin content (5.06%) was recorded in methanolic extract of T. officinale. Key words: Medicinal plants, Margalla Hills, qualitative, quantitative analysis.