Background: Cousinia Cass. is one of the most diverse genus of Asteraceae family. According to previous studies some Cousinia species showed significant cytotoxic activity. Purpose: In this study, we aimed to investigate the cytotoxic activity and phytochemical profile of four Cousinia species (C.davisiana Hub.-Mor., C.foliosa Boiss. & Balansa, C.ramosissima DC, C.stenocephala Boiss). Methods: The cytotoxic activity was investigated with SRB method against HepG2 (human hepatocellular carcinoma) cell line. The quantitative and qualitative determination of compounds were carried out by LC-MS/MS. Results: In a result, C. davisiana methanol extract (CD) and ethyl acetate sub-extract (CDE) showed more cytotoxic activity with 150 and 89 µg/ml IC50 values, respectively. The mass spectrums revealed the presence of 15 compounds in CD methanol extract and 9 compounds in active CDE sub-extract. According to quantitative analyses the highest contents of all compounds were detected in CD extract. Conclusion: Moreover, this study on inhibitory activity of CD extract and CDE sub-extract suggests detailed investigation for cytotoxic activity.