Objective: Thymoquinone, a monoterpene molecule which is derived from the volatile oil of Nigella sativa L. seed known as black seed “çörek otu” in Turkey, is a bioactive compound. Although it is consumed as food, it is claimed that thymoquinone has a wide range of effects, from its anticancer effect to its antiallergic effect, together with its main antioxidant property. Thymoquinone is thought to play an important role in the prevention and treatment of various types of cancers. Cisplatin, a platinum-based anticancer agent, has been used for many years in the treatment of solid tumors such as ovarian, cervix, testis, prostate, bladder and lung cancers despite its toxic effects. The use of plant extracts in combination with chemotherapeutic drugs in order to reduce the side effects of drugs used in chemotherapy and to increase their intra-body effects is the focus of research. The aim of this study is to reveal the cytotoxic effects of the combined use of thymoquinone, which is known to have important biological effects and whose importance has increased in recent studies, together with the anticancer drug cisplatin, on cervical cancer cells (HeLa). Material and Methods: HeLa cervical carcinoma cells provided from the American Type Culture Collection were used. The effects of thymoquinone in the concentration range of 1.95 μM-1000 μM and cisplatin in the concentration range of 0.49 μM - 250 μM on HeLa cell viability were measured by MTT method after 24 and 48 hours of incubation. After determining the IC50 values of each substance alone, the effects of combinations of thymoquinone with IC50 doses of cisplatin on cell viability were determined by MTT method after 24 and 48 hours of incubation. Results: In HeLa cells, for 24 h and 48 h incubations, IC50 values of thymoquinone were found to be 143.7 μM and 67.5 μM, respectively and IC50 values of cisplatin were found to be 20.3 μM and 12.9 μM, respectively. According to the study on the effects of the combined administration of thymoquinone on cisplatin cytotoxicity. Thymoquinone in the concentration range of 7.8-250 μM for 24 hours of incubation, statistically decreased the IC50 value of cisplatin (20 μM) in a dose-dependent manner (20.6%, 33.3%, 46.8%, 56.5%, 70.8%, 84.2% for 7.8 μM, 15.6 μM, 31.3 μM, 62.5 μM, 125 μM, 250 μM, respectively) in HeLa cells. Thymoquinone in the concentration range of 15.68-250 μM for 48 hours of incubation, statistically decreased the IC50 value of cisplatin in a dose-dependent manner (41.6%, 44.2%, 62.2%, 71.1%, 81.9% for 15.6 μM, 31.3 μM, 62.5 μM, 125 μM, 250 μM, respectively). Conclusion: In conclusion, our findings show that the combination of thymoquinone with cisplatin can increase the cytotoxicity of cisplatin in HeLa cells, and therefore it is thought that thymoquinone may increase the anticancer effect of cisplatin; however, to confirm their clinical use and to determine its interactions with anticancer drugs, the advanced in vitro and in vivo studies are needed.