The chemical composition of the essential oil obtained from Apium nodiflorum (L.) Lag. (Family Apiaceae), a plant used in the ethnomedical traditions of the Abruzzo region (Central Italy) as a culinary herb, as a diuretic, and to cure stomachache, was analyzed by gas chromatography/mass spectrometry, and 14 components were identified. Limonene (27.72 %), p-cymene (23.06%), myristicine (18.51%), and beta-pinene (6.62%) were the main components. The antimicrobial activity of the essential oil was assayed in vitro against Helicobacter pylori (strain DSMZ 4867), resulting in a minimum inhibitory concentration value of 12.5 microg/mL.