Superparamagnetic cobalt ferrite nanoparticles (CoFeO) possess favourite advantages for theranostic applications. Most of previous studies reported that CoFeO magnetic nanoparticles (MNPs) are suitable candidates for induction of hyperthermia and transfection agents for drug delivery. The present study synthesized and investigated the potential use of CoFeO as a contrast agent in magnetic resonance imaging (MRI) by using a conventional MRI system. The CoFeO were synthesized using co-precipitation method and characterized by TEM, XRD, FTIR, EDX and VSM techniques. Relaxivities and of CoFeO were then calculated using a 1.5 Tesla clinical magnetic field. The cytotoxicity of CoFeO was evaluated by the MTT assay. Finally, the optimal concentrations of MNPs for MRI uses were calculated through the analysis of weighted imaging cell phantoms. The superparamagnetic CoFe2O4 NPs with an average stable size of 10.45 nm were synthesized. Relaxivity , calculations resulted in suitable and / with values of 58.6 and 51 that confirmed the size dependency on relaxivity values. The optimal concentration of MNPs for MR image acquisition was calculated as 0.154 mM. Conclusion: CoFeO synthesized in this study could be considered as a suitable weighted contrast agent because of its high / value.