Background and Objective: Considering the increasing tendency of public towards green consumption and the dangers of artificial additives, this study aimed to assess antibacterial activity of essential oils of Cinnamomum zeylanicum, Mentha piperita L., Zataria multiflora Boiss and Thymus vulgaris against three important pathogenic and spoilage bacteria (Pseudomonas fluorescens, Erwinia carotovora and Escherichia coli).

• After obtaining the essential oils from Magnolia Co., their antimicrobial activity was assessed using broth microdilution method by determining the minimum inhibitory concentration (MIC50, MIC90) and minimum bactericidal concentration (MBC). All experiments were performed in triplicate and the data were analyzed using the GraphPad software and Duncan's new multiple range test.
• All essential oils showed antimicrobial activity in a concentration-dependent manner. Increasing the concentration of essential oils from 0.01% to 4% (v/v) significantly enhancing the antibacterial activity. The statistical calculations and comparison of data showed that the essential oils of C. zeylanicum and Z. multiflora performed better compared to  the other two essential oils, due to having lower values of MIC50 (≤0.1%), MIC90 (≤0.4%) and MBC (≤1%) (P <0.05).
• Considering the high antimicrobial activity of essential oils of C. zeylanicum and Z. multiflora, they can be used as effective food additives with fewer side effects. However, further studies are being conducted on the effectiveness of essential oils on the growth of other microorganisms and their results will be published soon.
• Essential Oils, Antimicrobial, Pathogenic Bacteria, Cinnamomum Zeylanicum, Zataria Multiflora Boiss.