Background: Prostate cancer is the second most prevalent and the sixth deadliest cancer among men worldwide. To improve the efficacy of radiotherapy on prostate cancer cells, we investigated the apoptosis-inducing effects of ionizing radiation (IR) in combination with auraptene (AUR). Methods and Results: PC3 cells were pretreated with various concentrations of the synthesized AUR and then were exposed to IR. After recovery, the viability of cells was determined by alamarBlue assay. Flow cytometric analysis with annexin V and propidium iodide was performed to assess apoptosis induction. Cell viability assay indicated that the toxicity of IR was enhanced by AUR, which was also confirmed by an increased number of apoptotic cells. The expression of P53, BAX, BCL2, GATA6, and CCND1 was analyzed by quantitative polymerase chain reaction (qPCR). qPCR demonstrated significant overexpression of P53 and BAX, while the expression of BCL2, GATA6, and CCND1 was significantly downregulated. Conclusion: These findings suggest that AUR is able to improve the apoptosis-inducing effects of IR in prostate cancer cells. Thus, this combinatorial treatment could be considered as a potential approach for further investigations.