Recently, the attention of researchers regarding Artemisia annua has been focused on the antimicrobial activity of the essential oil. This oil, rich in mono- and sesquiterpenes, has a strong activity against some Gram-negative and Gram-positive bacteria. The aim of our study is to further contribute to the knowledge of the antibacterial activity of an Artemisia annua essential oil collected in Tuscany and its three most represented compounds (artemisia ketone, 1,8-cineole and camphor). The essential oil obtained by hydrodistillation gave a yield of 0.37% (w/w fresh plant material). The composition of the essential oil extracted from flowering aerial parts was determined by gas chromatography (GC/FID and GC/MS). The essential oil and compounds were tested for activity against Escherichia coli O157, Salmonella Enteritidis, Salmonella Typhi, Yersinia enterocolitica and Listeria monocytogenes, all of which have great significance in foodborne infections. The antibacterial activity was tested using disk diffusion method and broth microdilution assay. The microorganisms tested were all sensitive to the A. annua essential oil in toto and to all its components, which often have lower activity than oil in toto.