Lippia adoensis var. koseret is a well- known medicinal plant endemic to Ethiopia. It has been traditionally used to treat different infectious diseases and also in food preparation as condiment. The focuse of the present paper was to evaluate antibacterial activities of methanol, petroleum ether, chloroform, ethyl acetate, butanol and aqueous extracts of leave of L. adoensis var. koseret against S. aureus E.coli and P. aeruginosa at two concentration level (5 and 10mg/ml) and Phytochemical and Thin Layer Chromatography analysis of the extracts showed antibacterial activity. The antibacterial assay was carried out using agar well diffusion method. Broth dilution method was used to determine the minimum inhibitory concentration. Phytochemical analysis was carried out using the standard phytochemical assays. Thin Layer Chromatography analysis of the methanol, petroleum ether and ethyl acetate extracts of the leaves was carried out using the solvent system Hexane: Ethyl acetate (in 7:3 ratios). The results of antibacterial assay revealed that methanol, petroleum ether and ethyl acetate extracts active against E.coli and P. aeruginosa. Among the tested microorganism S. aureus, was resistant to all extracts. The phytochemical screening revealed the presence of various chemical compounds like alkaloids, flavonoids, tannins and tannins. While, carbohydrate and amino acid were absent. Thin Layer Chromatography analysis of the methanol, petroleum ether and ethyl acetate fraction of the leaves of Lippia adoensis var. koseret revealed bands indicating the presence of various compounds that could act as potential antimicrobial agents.