In this study, the cytotoxic, genotoxic/antigenotoxic and antioxidant/oxidant activity of copaene (COP), a plant-derived tricyclic sesquiterpene, on human lymphocyte cultures (n = 5) was investigated. COP was added into culture tubes at various concentrations (0, 10, 25, 50, 100, 200 and 400 mg/L). While the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays were used for viability and cytotoxic evaluations, the micronucleus (MN) and sister chromatid exchange (SCE) assays were used for genetic evaluations. Moreover, total antioxidant capacity (TAC) and total oxidative status analysis were used for biochemical evaluations. According to LDH and MTT assays COP significantly reduced cell proliferation at high concentrations (200 and 400 mg/L). In addition, there was no significant increase (P < 0.05) in both SCE and MN frequencies of cultures treated with COP as compared to controls. We have also concluded that concentrations of COP of 50 and 100 mg/L increased TAC level when compared to the controls. In conclusion, in this study it has been reported for the first time that copaene is not genotoxic and it increases the antioxidant capacity in human lymphocyte cultures.