Increasing bacterial resistance to commercial antibiotics has led to considering medicinal herb applications. This study aimed to identify chemical composition of essential oil of some native medical herbs and their antibacterial activity against Yersinia ruckeri compared with Enrofloxacin in in vitro experiments. The antibacterial activities of ethanolic extracts and essential oils of Eryngium campestre, Pimpinella affinis, Mentha piperita, Achillea wilhelmsii and Cuminum cyminum were analyzed by disk diffusion, Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) methods in in vitro. Also, the oil constituents of the mentioned plants were analyzed by gas chromatography. The MIC value of the ethanolic extracts and essential oils were 31.2-500 µg/mL and 15.6-250 µg/mL, respectively, while the MBC of the mentioned extracts and essential oil were 62.4-500 µg/ml and 31.2-250 µg/ml, respectively. The results showed that the C. cyminun, E. campestre and M. piperita could be introduced as more effective antimicrobial candidates to aquaculture industry.