Radiotherapy (RT), which is a therapeutic treatment modality that is commonly used for cancer, employs high‐energy irradiation to induce the generation of reactive oxygen species (ROS) and to cause DNA damages. Nevertheless, the therapeutic efficacy of RT is predominantly constrained due to inadequate DNA damage in malignancies and deleterious impacts on healthy tissues. In the current study, bovine serum albumin (BSA)–coated AgBiS2 nanodots, also known as AgBiS2@ BSA nanodots, were developed for enhanced breast cancer treatment. This was accomplished by the use of an extremely simple and eco‐friendly method. Both scanning transmission electron microscopy (STEM) and scanning electron microscopy (SEM) images revealed that prepared nanoradiosensitizers, AgBiS2@ BSA, were spherical in shape and uniformly distributed. AgBiS2@ BSA nanodots possessed excellent biocompatibility and exhibit excellent monodispersity as well. Furthermore, in vitro assays such as MTT, colony formation assay, and intracellular ROS generation assay revealed the significant cell inhibitory impact of the produced AgBiS2@ BSA nanodots under X‐ray irradiation under X‐ray irradiation. Remarkably, the combined administration of AgBiS2@ BSA nanodots along with X‐ray irradiation increased ROS level within cells by increasing the localized radiation dosage and improving the anti‐tumor effectiveness of RT.