Objective: Cancer is one of the most important diseases today. The use of chemical drugs, surgical operations, and transplants is very common in its treatment. In addition to these treatment methods, studies include the effects of natural and plant-derived substances. Various substances are used in these studies, which are called phytotherapy. The antioxidant activity and cytotoxic effects of Cocos nucifera on hepatocellular carcinoma HepG-2 and the mouse fibroblast L929 cell line were investigated in this study. Methods: In this study, in vitro cytotoxic effects of C. nucifera at different concentrations (7.81-500 mg/ml) were investigated on the L929 Mouse Fibroblast cell line and HepG-2 Hepatocellular Carcinoma cell line. In addition to these studies, their antioxidant capacity was evaluated via spectrophotometric methods. In this work, different concentrations of C. nucifera were examined. Results: According to the results, C. nucifera had a cytotoxic effect in HepG-2 and ensured the proliferative effect of cells in the L929 cell line. Among C. nucifera extracts according to total antioxidant capacity results, C. nucifera extract was found to be the richest in antioxidants with 2.79 mmol/L, while the material with the lowest antioxidant capacity was determined to be C. nucifera milk. DPPH free radical scavenging activity results show the opposite. Conclusion: In line with the data we obtained, it is thought that C. nucifera can be used in liver cancer studies, and its antioxidant effect may play an important role in balancing against oxidative stress. Simultaneously, the data show that the exposure time and concentrations of the active substance are related to the cytotoxic effect. However, it may be considered that the use of C. nucifera water, extract, and milk in cancer patients may be supported by more comprehensive clinical studies.