Centaurea species of Asteraceae family are widely use in traditional medicine. Despite wide medicinal use of Centaurea sp., there is limited knowledge concerning Centaurea behen toxicity. Therefore, in this study, it is aimed to determine cytotoxic and oxidative effects of essential oil of C. behen on human blood cell cultures. 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) release assays were performed to determine cytotoxic effects. In addition, total antioxidant capacity (TAC) and total oxidative status (TOS) were examined to determine oxidative potentials. The results indicated that all tested concentrations of essential oil of C. behen were cytotoxic and led to decreases of cell viability in both assays. Besides, C. behen led to significant increases of TOS levels and decreases of TAC levels. As a conclusion, the present study showed for the first time the cytotoxic and oxidant effects of essential oil of C. behen on cultured human whole blood cells.