Ionizing radiation (IR) may induce oxidative-stress-related molecular changes (DNA damage, cell death, etc.) in living organisms by affecting them directly and indirectly in a time- and dose-dependent manner. This study was planned to present the effects of thymoquinone (TQ) in preventing oxidative stress, DNA damage and apoptotic cell death that may occur after IR exposure. For this purpose, hFOB 1.19 osteoblast cells were used. Using the MTT viability test, the dose of IR reducing the proliferation of cells and the concentration of TQ increasing cell proliferation the most were determined. Five groups were formed as the Control (C), Thymoquinone (TQ), Ionizing radiation (IR), Ionizing radiation + Thymoquinone (IR + TQ) and Thymoquinone + Ionizing radiation (TQ + IR) groups. By applying the determined concentrations on the cells, DNA damage level was determined with the Comet assay, and the gene expression levels of enzymes effective in the oxidative and apoptotic mechanisms were determined with the RT-qPCR method expression. It was determined that, as a result of IR application for 24 and 72 h, DNA damage occurred in the osteoblast cell line. While no significant change was observed in the oxidative and apoptotic gene expression levels at the end of 24 h, an increase in comparison to the control group was determined in the Sod-1 (2.4-fold), Caspase-3, and Caspase-9 gene expression levels at the end of 72h. . Application of TQ in 72 h of incubation before and after IR application significantly reduced the expression levels of Caspase-3, Caspase-9, and DNA damage together with the increased GPx-3 and Sod-1 gene expression.Consequently, it was seen that IR application affected apoptotic and oxidative stress-regulating genes in the hFOB 1.19 osteoblast cell line in a time- and dose-dependent manner, and it was thought that the harmful effects on this cell line may have been caused by the activation of the mitochondrial pathway. It was determined that TQ significantly reduced the gene expression values that changed due to IR and brought them close to those of the control group, and it was concluded that TQ became useful by showing antioxidant properties against the harmful effects of IR.