Nanosized complexes of ferromagnetic particles with a photodithazine sensitizer (used in photodynamic therapy in oncology) have been synthesized and investigated using small-angle neutron scattering for the first time. The structure of the complexes has been determined, and the influence of the biocompatible polymer Pluronic on their structure has been analyzed. The possibilities of using the complexes for magnetically guided delivery of the photosensitizer to cells and tissues in the treatment of oncological diseases by photodynamic therapy have been discussed.