Glioblastoma Multiforme (GBM), which is a common and primary brain tumor in adults, is an important cause of death worldwide as an aggressive and treatment-resistant cancer tumor. In this cell culture study, the apoptotic and anti-proliferative effects of borax and irinotecan at different doses, alone or in combination, were investigated in the YKG1 cell line. Cytotoxic activities were analyzed by MTT method and TUNEL staining after 24th and 48th hours of incubation with borax administered at doses of 1mg and 3mg per ml; irinotecan 50mM and 100mM. Both irinotecan and borax have been shown to induce apoptosis when used alone, and thus cause anti-proliferation. It was determined that these effects were potentiated by the combined application of the agents. In addition, it was determined that this effect in combined applications was more pronounced after 48 hours and at higher doses. In light of the data obtained, the combination of irinotecan with borax to increase the cytotoxic effect of irinotecan, which is used in many different cancer types, can be tried in further prospective studies.