Avicenniaceae family is a member of true mangrove plants, which has one genus, 11 species and several sub species. Avicennia marina (Forssk) Vierh is the most current species among these plants in Iranian mangrove forest. Penicillium expansum is the most devastating pathogen of apple fruit, being responsible for about 90% of production losses during post-harvest handling. The aim of this study was to determine antifungal effect of the aqueous and ethanolic extracts of Avicennia marina (different concentrations) on Penicillium expansum” in vitro”. In this study, antimicrobial effect of the extracts was evaluated by two methods, “Collins method” (spreading of the extract on medium surface) and “disk agar diffusion method” at 10, 20, 30 and 40 mg/ml.The Minimum Inhibitory Concentration (MIC) and Minimum Fungicidal Concentration (MFC) for both species was determined using a dilution method. Statistical analysis was carried out by analysis of variance (ANOVA). The results showed that the ethanolic extract had inhibition effect on Penicillium expansum in both "disk agar diffusion assay" and “Collins method”, but the aqueous extract in both "disk agar diffusion assay" and “Collins method” did not show any inhibition effect on Penicillium expansum. The result showed that MIC of Avicenna marina leaves of the aqueous and ethanolic extracts for Penicillium expansum was 32 and 16 mg/ml respectively. The aqueous and ethanolic extracts MFC of Avicenna marina leaves for Penicillium expansum was 64 and 32 mg/ml respectively. The ethanolic extract of Avicenna marina leaves “in vitro” had a significant antifungal effect on Penicillium expansum. Results showed that Avicenna marina extract can be used as a natural antimicrobial in food products

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