© 2022Janus heterostructures based on bimetallic nanoparticles have emerged as effective radiosensitizers owing to their radiosensitization capabilities in cancer cells. In this context, this study aims at developing a novel bimetallic nanoradiosensitizer, Bi2S3-Fe3O4, to enhance tumor accumulation and promote radiation-induced DNA damage while reducing adverse effects. Due to the presence of both iron oxide and bismuth sulfide metallic nanoparticles in these newly developed nanoparticle, strong radiosensitizing capacity is anticipated through the generation of reactive oxygen species (ROS) to induce DNA damage under X-Ray irradiation. To improve blood circulation time, biocompatibility, colloidal stability, and tuning surface functionalization, the surface of Bi2S3-Fe3O4 bimetallic nanoparticles was coated with bovine serum albumin (BSA). Moreover, to achieve higher cellular uptake and efficient tumor site specificity, folic acid (FA) as a targeting moiety was conjugated onto the bimetallic nanoparticles, termed Bi2S3@BSA-Fe3O4-FA. Biocompatibility, safety, radiation-induced DNA damage by ROS activation and generation, and radiosensitizing ability were confirmed via in vitro and in vivo assays. The administration of Bi2S3@BSA-Fe3O4-FA in 4T1 breast cancer murine model upon X-ray radiation revealed highly effective tumor eradication without causing any mortality or severe toxicity in healthy tissues. These findings offer compelling evidence for the potential capability of Bi2S3@BSA-Fe3O4-FA as an ideal nanoparticle for radiation-induced cancer therapy and open interesting avenues of future research in this area.