Abstract: The volatile chemical constituents of Lemon verbena, Aloysia triphylla were extracted by modified steam distillation method and determined by gas chromatography-mass spectroscopy (GC-MS). Forty-three components were separated and 35 of them were determined qualitatively and quantitatively, which represented about 96.05%. The major component was citral (14.21%) and seven components were identified as main components (more than 4%) i.e., β-caryophyllene (10.71%), 1, 8-cineole (9.1%), Citronellol (8.87%), iso-menthone (6.43%), α-bergamotene (5.33%), menthonol (5.10%) and p-cymene (4.23%). The resulting oil was tested for its radical scavenging activity employing 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. Through all concentrations (5, 10 and 15 μL) for DPPH assay moderate radical scavenging activity compared to BHA. A. triphylla essential oil was tested against six Gram-positive and Gram-negative bacteria and four phytopathogenic fungi. A. triphylla essential oil exhibited an interesting antibacterial activity against Bacillus subtilis and Staphylococcus aureus. No antibacterial activity was observed against Listeria monocytogenes, Salmonella spp. and Escherichia coli. A. triphylla essential oil partially inhibited the growth of the fungal strains was observed against Candida albicans, Phanerochaete chysosporium and Trichoderma reesei. No antifungal effect was observed against Trichoderma viride.