Great challenges still remain in the management of patients with castration-resistant prostate cancer (CRPC) based on traditional treatments, and the rapid development of nanotechnology may find a breakthrough. Herein, a novel type of multifunctional self-assembly magnetic nanocarriers (IR780-MNCs) containing iron oxide nanoparticles (Fe3O4NPs) and IR780 iodide was synthesized by an optimized process. With a hydrodynamic diameter of 122 nm, a surface charge of –28.5 mV and the drug loading efficiency of 89.6%, IR780-MNCs have increased cellular uptake efficiency, long-term stability, ideal photothermal conversion ability and excellent superparamagnetic behavior. The in vitro study indicated that IR780-MNCs have excellent biocompatibility and could induce significant cell apoptosis under the 808 nm laser irradiation. The in vivo study showed that IR780-MNCs highly accumulated at the tumor area could reduce the tumor volume of tumor-bearing mice by 88.5% under the 808 nm laser irradiation, but minimal damage to surrounding normal tissues. Since IR780-MNCs encapsulated a large number of 10 nm homogeneous spherical Fe3O4NPs, which can be used asT2contrast agent, the best window for photothermal therapy can be determined through MRI. In conclusion, IR780-MNCs have initially showed excellent antitumor effect and biosafety in the treatment of CRPC. This work provides novel insights into the precise treatment of CRPC by using a safe nanoplatform based on the multifunctional nanocarriers.