Phytochemical investigation of Cephalaria tuteliana (Caprifoliaceae) endemic to Turkey was carried out for the first time. Thirteen compounds were isolated, including 2 triterpenoid sapogenins, 10 saponins, and 1 iridoid glycoside. This is the first report of the isolation of pomolic acid, tormentic acid, and 3-O-alpha-L-rhamnopyranosyl-(1 -> 3)-beta-D-glucopyranosyl hederagenin, not only from the Cephalaria genus, but also from the Caprifoliaceae family. The structures of the isolated compounds were elucidated by a combination of spectroscopy, including one- and two-dimensional nuclear magnetic resonance, and by comparison with the reported data in the literature. Two triterpene sapogenins, hederagenin and oleanoic acid, the latter being the most typical sapogenin of the oleanane type of triterpene saponins, were evaluated by the MTT method for their cytotoxic effect against A549, HeLa, PANC1, and SHSY5Y cancer cells, and the noncancerous HEK293 cell line. The cytotoxic activity of triterpene aglycones was discussed in detail and a structure-activity relationship was established. C. tuteliana may be considered as a useful source for developing new cytotoxic and immunotherapeutic agents due to its biologically active saponin content.