Purpose <p>A reliable imaging probe is essential for the accurate diagnosis of diseases and to support effective therapeutic decision-making. Different nanoparticles based multimodal probes have been studied for bone imaging. This work focuses on synthesizing of radiolabeled iron oxide magnetic nanoparticles as a promising dual modality bioprobe (SPECT/MR) for bone imaging.</p> Methods <p>In this work, silica coated magnetic nanoparticles (SiO₂@MNPs) were synthesized. Radioiodination of SiO₂@MNPs with iodine − 131 was performed via the Finkelstein reaction to produce a prospective radioiodinated MNPs for bone targeting.</p> Results <p>The radioiodinated NPs were obtained in high radiochemical purity (about 98.5 ± 0.5%) by magnet separation. The aqueous dispersion of the radioiodinated silica coated MNPs (¹³¹I-SiO₂@MNPs) exhibited adequate in-vitro stability and biocompatibility. Biodistribution study results after intravenous injection of (¹³¹I-SiO₂@MNPs) in normal mice revealed the high bone targeting efficiency of the radiolabeled NPs (C_max= 6± 0.5% ID/g at t_max= 2&#xa0;h post injection). Magnetization properties measurements proved the preservation of the magnetic properties of SiO₂@MNPs after the iodination process retaining its effectiveness as MRI contrast agent.</p> Conclusion <p>Based on to the results of this study, ¹³¹I-SiO₂@MNPs could be considered as a promising candidate for SPECT/MR dual bone imaging.</p> Graphical Abstract <p></p>