Thevetia peruviana (Pers.) K. Schum is one of the important medicinal as well as ornamental plant belongs to the Dogbane family Apocynaceae. It is commonly known as yellow oleander. The plant is popular in traditional medicine especially for treatment of heart problems. The leaves are emetic and purgative. Leaf decoction is given to prevent conception. The ethanolic leaf extract of Thevetia White was tested for antimicrobial activity against human pathogenic bacteria. Thevetia White leaf extract showed strong antimicrobial activity against Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris, Pseudomonas aeruginosa and Salmonella typhi. The phytochemical analysis reveals the presence of alkaloids, flavanoids, cardiac glycosides, phenolic compounds, phytosterols and tannins, which are mainly contributed to antimicrobial activity and medicinal utility of the plant.