The lemongrass essential oil (LEO) extracted from the leaf of lemongrass (Cymbopogon citratus) was tested for its inhibitory effects against three pathogenic bacteria (Escherichia coli, Staphylococcus aureus, and Vibrio cholerae). This research used a Completely Randomized Design with 5 treatments of LEO concentration in 1% tween 80, namely 1%, 2%, 3%, 4%, 5% (v/v). By using of GC-MS to determine LEO chemical composition, the LEO was composed of several compounds which citral, a monoterpene compound, was the dominant compound. This LEO could inhibit significantly the growth of E. coli, S. aureus and V. cholerae. The most sensitive of the bacteria against the LEO was Vibrio cholerae. In addition, the minimum inhibitory concentration (MIC) of LEO was 1.0%, 0.8%, and 0.6% respectively against E. coli, S. aureus, and V. cholera.