There are several attractive opportunities for using magnetic nanomaterials for anticancer applications. Herein, a magnetic nanomaterial platform is successfully developed based on natural Fe3O4 magnetosomes extracted from the bacterium Magnetospirillum magneticum AMB-1 for anticancer therapy. The authors initially functionalize the magnetosome membranes in situ with gold nanoparticles to construct an attractive core-satellite structure. Subsequently, the physical properties and application potentials of these structures are characterized as contrast agents for photoacoustic imaging and magnetic resonance imaging and as therapeutic agents with selective magnetic field guidance for diverse antitumor modalities, including starving, chemodynamic, and photothermal therapies. Owing to the high-performance imaging-guided synergistic effect, only a single injection and single laser irradiation result in excellent therapeutic efficacy against tumor growth in multiple cell-derived xenograft tumor models and, most notably, patient-derived organoid and patient-derived xenograft tumor models. The demonstrations of the use of natural magnetic nanomaterials to achieve strong and synergistic antitumor performances highlight the promising application potential of this flexible and easy-to-prepare platform for developing innovative treatments for diseases in humans.