The whole plant material of Mirabilis jalapa was collected from Kolli hill (Eastern Ghats), Namakkal District, Tamilnadu, India.Screening of phytochemical analysis and antimicrobial activity was carried out according to standard protocols. The present research work revealed that the antimicrobial activity of methanolic extract of Mirabilis jalapa L. is associated with the presence of certain phytoconstituents such as flavonoids, alkaloids, phenolic compounds, tannins or some other phytochemicals. However the present attempt is preliminary and a pioneer study for this plant. The detailed research work the possibility for further studies on the isolation of phytoconstituents and their inhibitory activity. Preliminary phytochemical analysis showed the phytochemical constituents, but maximal amounts of alkaloids, flavonoids and terpenoid were identified for the methanolic extract.