Nowadays, many antibiotics are being used to control infectious diseases. Inappropriate use of antibiotics leads to emergence of resistant bacteria and problems such as a prolonged course of treatment. Medicinal plants and their derivatives, as a good source of treatment, are effective against drug resistance. In this study we have evaluated the antimicrobial activity of herbal essential oils of four medicinal plant Cuminum cyminum, Satureja hotensis L, Citrus limon and Mentha piperita. For preparation of herbal essential oils clevenger apparatus was used, and the active components of the herbal essential oils were determined by GC-MS. In order to observe the effects of the essential oils, they were examined on Staphylococcus aureus, Escherichia coli and Salmonella typhi using disc diffusion method in vitro. Also, the Minimal Inhibitory Concentration (MIC) and Minimal Bactericide Concentration (MBC) of each essential oil was measured and compared with commonly used antibiotics. Obtained results showed that all of the essential oils possess inhibitory and antibacterial effects, but the Mentha piperita essential oil showed a better effect in comparison to other used essential oils. It was concluded that all the herbal species demonstrate antibacterial properties, but the level of bacterial growth inhibition induced by plant materials, shown to be dependent on herbal source and bacterial strain.