To investigate Phytochemical analysis and in-vitro antimicrobial activity of leaf extract of Allamanda cathartica linn Plants have been the major source of drugs in medicine and other ancient systems in the world. In traditional systems of medicine, Indian medicinal plants have been used in the successful management of various disease conditions. Allamanda cathartica (AC)Linn. (Apocynaceae) is one of the most studied species of the Allamanda genus. This method has been by using aqueous methanol(80% solvent) and was evaluated for phytoconstituents present in them so the preliminary phytochemical screening method was done with the help of standard literature. The Aqueous Methanolic extract of AC consists of alkaloids, carbohydrates, glycosides, tannins, phytosterols, flavonoids, and phenols. So the present study provides evidence that it is having a moderate antimicrobial effect on organisms E coli, Strephylococcus aureus, and candid albicans Allamanda cathartica contains medicinally important bioactive compounds and it is having a moderate antimicrobial effect on organisms E coli, Strephylococcus aureus, Candida albicans. We suggest for extensive research studies on the plant and formulations should be encouraged with proper evaluation.