DNA interaction with disulfophthalocyanine of cobalt (CodSPC) was studied by UVVIS spectrophotometry and low gradient viscometry. The thermal denaturation of DNA in complexes with CodSPC was compared with free DNA denaturation. The small increase in melting temperature indicates that the secondary structure of DNA in complexes is stable. As a results of experimental research the external binding of CodSPC to DNA was determined. The only one type of binding is accompanied by stacking of heterocycles at high concentrations of CodSPC. An increase in viscosity of DNA solutions with the growth of CodSPC concentration can be explained by intermolecular DNA contacts via CodSPC.