X‐rays are rays that penetrate the human tissue and are capable of penetrating water, air, and oxygen in various biological tissues or tumors. In recent years, significant progress has been made in the research of X‐ray‐excited luminescent materials for cancer diagnosis and treatment. In this study, the application of X‐ray‐excited luminescent materials is reviewed for tumor imaging and therapy. First, two classes of luminescent materials are briefly introduced for a form of enhanced X‐ray computed tomography, X‐ray‐excited optical luminescence imaging. Subsequently, the design of multifunctional hybrid materials is evaluated for radiotherapy and other treatments and their synergistic effects under X‐ray excitation are studied. Finally, current key issues and solutions in the field are discussed in detail.