One of the negative effects of ionizing radiation is the alteration of cellular signaling pathways which lead to carcinogenesis and tumorigenesis. In this review, we discussed the impacts of ionizing radiation on cells and cellular signaling pathways. In this regard, exposure to radiation can directly or indirectly alter cellular signaling pathways. Remarkably, irradiated cells release special mediators into cellular matrix, aberrating cell-cell and cell-environment interactions. Most notably, these mediators include nitric oxide (NO), reactive oxygen species (ROS), and cell growth factors which contribute to cellular interactions between irradiated cells and their neighbor cells, a phenomenon known as radiation-induced bystander effect. DNA molecule is the most important cellular compartment damaged by ionizing radiation. On the other hand, the ability of irradiated cells to repair the damaged DNA is very low. Therefore, DNA alternations are passed to the next generations, and ultimately lead to carcinogenesis. The study of ionizing radiations and their impacts on biological systems is of remarkable importance to divulge their impacts on cellular signaling pathways.