Antifeedant activities of Tanacetum cadmeum ssp. cadmeum, Tanacetum parthenium, Tanacetum corymbosum ssp. cinereum, Tanacetum chiliophyllum var. chiliophyllum, Tanacetum kotschyi and Tanacetum cadmeum ssp. orientale were assessed on Spodoptera littoralis Boisd. (Lep: Noctuidae) third instar larvae. The highest antifeedant activities were found as 62 and 55.05% in the extracts of MeOH with T. cadmeum ssp. cadmeum aerial parts, MeOH with T. corymbosum ssp. cinereum flowers, respectively. Bioassay guided investigations on Tanacetum cadmeum ssp. cadmeum afforded three eudesmanolides; artesin (1), taurin (2), and artemin (3), three germacranolides; tavulin (4), tanachin (5), and tamirin (6), the coumarin; scopoletin (7), and two flavonol derivatives; tanetin (6-hydroxykaempferol 3,7,4′-trimethylether) (8) and 6-hydroxykaempferol 3,6-dimethylether (9). The structures of the compounds were elucidated by spectral methods, such as IR, UV, 1 H NMR and 13 C NMR (COSY, APT, DEPT, HMQC, HMBC, NOE, X-ray, EIMS, CIMS and HRMS). In this paper, the antifeedant activities of some Tanacetum species and the compounds isolated from T. cadmeum ssp. cadmeum are reported.