Nanosized complexes of ferroparticles with a sensitizer photoditazin (used in photodynamic therapy in oncology) have been synthesized and studied by small-angle neutron scattering. The structure of the complexes was determined, and the influence of the biocompatible polymer pluronic investigated. Clinical tests revealed increased efficiency of the complexes compared with the starting photoditazin. The complexes can be used as the first magnetically operated sensitizer for treatment of oncological diseases by photodynamic therapy.