The chemical composition and plant pathogenic antifungal activity of tea tree essential oils (Melaleuca alternifolia) collected in Long An, Vietnam was surveyed. By gas chromatography and mass spectrometry (GC-MS), the main chemical composition in tea tree essential oils was identified to be eucalyptol with a concentration of 31.54%. Plant antifungal activity of tea tree essential oils was evaluated with many kinds of dissolvent to determine the minimum inhibitory concentration (MIC). The results showed that tea tree essential oils had the ability to inhibit the growth of five phytopathogenic fungal strains: Aspergillus niger, Corynespora cassiicola, Colletotrichum sp., Fusarium oxysporum and Pyricularia oryzae with the minimum inhibitory concentrations (MICs) were in the range of 6 ? 8 μL mL-1.