Due to the increased incidence and population growth that has been leading to growing number of cases worldwide, early diagnosis and treatment of cancer is crucial. Low density cancer tissue cannot be diagnosed before progressing toward a metastatic stage. Thus, theranostic systems play a significant role in assisting timely diagnosis and treatment. The combination of magnetic resonance imaging (MRI) and computed tomography (CT) contrast agents in a single probe is of high importance and necessity, where individual strengths of each approach can be merged while shortcomings of each modality could be compensated. With this motivation, we have developed and synthesized Bi2S3@BSA-Fe3O4 nanoparticles as a dual MRI/CT contrast agent and carrier of curcumin (CUR) as natural anticancer drug. The nanoparticles shortened both the longitudinal (T-1) and transverse (T-2), MRI relaxation times, with a more distinct effect on producing negative contrast (T-2) images with a relaxivity (r(2)) of 54.73 mM(-1) s(-1). The magnetite/bismuth hybrid nanoparticle also was capable of increasing CT image contrast. Further, in vitro cytotoxicity assay showed high biocompatibility of the synthesized nanoparticles. Furthermore, in vitro cytotoxicity assay on cancer cells showed high anticancer activity of the synthesized nanoparticles.