Abstract: Aromatic and medicinal plants are widespread throughout world. Essential oils obtained from different aromatic and medicinal plants parts have been shown antibacterial, antifungal, antiviral and antioxidant properties The experiment was started in season 2010-2011. This work was conducted for determination of the phytochemistry and antibacterial activity of the essential oil from leaves of Thymus vulgaris and Tanacetum parthenium growing in Iran. Antibacterial effects of the extracts were tested on six Gram-positive and nine Gram-negative human pathogenic bacteria. The major compounds in the leaves of Thymus vulgaris and Tanacetum parthenium were α-pinene followed by camphene, β- pinene, 1,8-cineole, camphor, thymol and carvacrol. The results of the Minimal Inhibiting Concentration (MIC) and Minimum Bactericidal Concentration (MBC) varied from one bacterium to another. The highest and broadest activity was shown by Thymus vulgaris oil. Thymol and carvacrol possessed the highest antibacterial activity among the tested components.