The chemical composition of the essential oils of the flowering parts and of the hexane extracts of the leaves, of three species of the genus Ferulago (Apiaceae) from Greece, i.e., F. thyrsiflora, F. sylvatica and F. nodosa, was analysed by GC and GC-MS. Manoyl oxide isomers and lupanine, were identified in the hexane extracts of F. thyrsiflora. Dillapiole, was identified in all hexane extracts. Ent-3 beta-hydroxy-13-epi-manoyl oxide was identified and isolated from the essential oil of F. thyrsiflora. All these compounds are new reports for the genus Ferulago and are useful chemotaxonomic markers. Chemical data of F. thyrsiflora is presented for the first time. The essential oils and the extracts were investigated for their antimicrobial activity against Gram-positive and Gram-negative microorganisms.