Abstract Leaf essential oil of Coleus aromaticus (Lamiaceae) from Cambodia was steam-distilled and investigated for its percentage composition and antibacterial activity against ffteen oral microflora pathogen strains. The volatile oil sample investigated in this work contained mainly thymol (57.4%), carvacrol (13.5%), γ-terpinene (5.6%), and p-cymene (5.2%). The in vitro antibacterial experiments revealed that on tested bacteria the minimum inhibitory concentration (MIC) ranged 40â80 µL/Land the minimum bactericidal concentration (MBC) 80â150 µL/L. These findings support the idea that the C. aromaticus essential oil sample tested here could be suitable for use as a natural active ingredient in natural and low-cost drugs against oral microflora.