In this study, Bi₂O₃ nanoparticles were employed as computed tomography (CT) contrast agents. In this regard, X‐ray attenuation of Bi₂O₃ nanoparticles, prepared via DC arc discharge in water, was investigated. In addition, the optical, structural, morphology and cytotoxicity properties of afforded nanoparticles were also studied. The electric arc discharge was done via bismuth electrodes in a water medium. Then, to stabilise Bi₂O₃ nanoparticles, chitosan molecule was cross linked via glutaraldehyde around Bi₂O₃ nanoparticles. X‐ray diffraction analysis demonstrated the monoclinic structure and field emission‐scanning electron microscopy images clarified the average size of Bi₂O₃ as 40 nm. Fourier transform infrared analysis proved chitosan band formation around Bi₂O₃ nanoparticles. The 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay revealed no considerable toxicity after 72 h. Finally, X‐ray CT of chitosan‐coated Bi₂O₃ nanoparticles and Iohexol was carried out at concentrations of 1–6 mg/ml. The CT number of chitosan‐coated Bi₂O₃ nanoparticles measured 16, 30, 49, 66, 75 and 85, as well as, respective numbers for Iohexol were 5, 14, 25, 34, 44 and 57. Therefore, it displayed that X‐ray attenuation of chitosan‐coated Bi₂O₃ nanoparticle was more in comparison with Iohexol at the same concentrations. Eventually, the results demonstrated that chitosan‐coated Bi₂O₃ nanoparticles are a suitable candidate for commercial iodine contrast agent substitution.