Complexes of superparamagnetic nanoparticles of magnetite with porphyrins, i.e., sulfonated tetraphenylporphine dihydrochloride (H2TPPS4(HCl)2) and photodithazine (used in photodynamic therapy for treatment of oncological diseases), in an aqueous medium have been synthesized for the first time and investigated using small-angle neutron scattering and spectrophotometry. The influence of the biocompatible polymer Pluronic on the functional properties of the synthesized complexes has also been analyzed. It has been shown that the synthesized complexes of ferrofluids with photodithazine and Pluronic exhibit a high efficiency as compounds capable of suppressing the reproduction of tumor cell cultures. The results obtained can be used in the design of a magnetically guided drug for photodynamic therapy.