Radiation-induced lung injury (RILI), including acute radiation pneumonitis and chronic radiation-induced lung fibrosis, is the most common side effect of radiation therapy. RILI is a complicated process that causes the accumulation, proliferation, and differentiation of fibroblasts and, finally, results in excessive extracellular matrix deposition. Currently, there are no approved treatment options for patients with radiation-induced pulmonary fibrosis (RIPF) partly due to the absence of effective targets. Current research advances include the development of small animal models reflecting modern radiotherapy, an understanding of the molecular basis of RIPF, and the identification of candidate drugs for prevention and treatment. Insights provided by this research have resulted in increased interest in disease progression and prognosis, the development of novel anti-fibrotic agents, and a more targeted approach to the treatment of RIPF.