Essential oils have been used for centuries ago in traditional medicine, for industrial applications and as food preservatives due to their antimicrobial activity. The antibacterial activity of essential oil of cumin, black seedss, marjoram, rosemary and sage were tested against Gram-negative bacteria (Escherichia coli O157 :H7, Klebsiella pneumonia, Proteus vulgaris, Pseudomonas aeruginosa, Salmonella typhi and Serratia marcescens) and Gram-positive bacteria (Bacillus anthrakoids, Bacillus cereus, Bacillus subtilis, Listeria monocytogenes, Micrococcus luteus Micrococcus roseus, Staphylococcus aureus and Streptomyces sp. ) in vitro by Well agar diffusion method. The results showed that, the essential oil of cumin and marjoram had the best inhibitory effect against tested bacteria. Meanwhile, the essential oil of rosemary exhibited good antibacterial effect against all of these tested bacteria except Listeria monocytogenes and Pseudomonas aeruginosa. Also, essential oil of black seedss and sage showed similar inhibitory effect against tested bacterial species. These essential oils may be used not only to enhance the product flavor but also to inhibit and delays the microbiological growth. Hence they may be considered as natural preservatives.