Phototheranostic　nanoplatforms　are　of　particular　interest　for　cancer　diagnosis　and　imaging-guided　therapy.　Herein,　we　develop　a　supramolecular　approach　to　fabricate　a　nanostructured　phototheranostic　agent　through　the　direct　self-assembly　of　two　water-soluble　phthalocyanine　derivatives,　PcS4　and　PcN4.　The　nature　of　the　molecular　recognition　between　PcS4　and　PcN4　facilitates　the　formation　of　nanostructure　(PcS4-PcN4)　and　consequently　enables　the　fabrication　of　PcS4-PcN4　with　completely　quenched　fluorescence　and　reduced　singlet　oxygen　generation,　leading　to　the　high　photoacoustic　and　photothermal　activity　of　PcS4-PcN4.　In　vivo　evaluations　suggest　that　PcS4-PcN4　could　not　only　efficiently　visualize　a　tumor　with　high　contrast　through　whole-body　photoacoustic　imaging　but　also　enable　excellent　photothermal　therapy　for　cancer.　©　2020　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim