Imaging-guided　chemo-phototherapy　based　on　a　single　nanoplatform　has　a　great　significance　to　improve　the　efficiency　of　cancer　therapy　and　diagnosis.　However,　high　drug　content,　no　burst　release　and　real-time　tracking　of　nanodrugs　are　the　three　main　challenges　for　this　kind　of　multifunctional　nanotheranostics.　In　this　work,　we　developed　an　innovative　theranostic　nanoplatform　based　on　a　Pt(iv)　prodrug　and　a　near-infrared　(NIR)　photosensitizer.　A　Pt(iv)　prodrug　and　a　cyanine　dye　(HOCyOH,　Cy)　were　copolymerized　and　incorporated　into　the　main　chain　of　a　polyprodrug　(PCPP),　which　self-assembled　into　nanoparticles　(NPs)　with　∼27.61%　Cy　loading　and　∼9.37%　Pt　loading,　respectively.　PCPP　NPs　enabled　reduction-triggered　backbone　cleavage　of　polyprodrugs　and　bioactive　Pt(ii)　release;　Cy　could　be　activated　under　808　nm　laser　irradiation　to　produce　local　hyperthermia　and　reactive　oxygen　species　(ROS)　for　phototherapy.　Moreover,　PCPP　NPs　with　extremely　high　Cy　and　Pt　heavy　metal　contents　in　the　backbone　of　the　polyprodrug　could　directly　track　the　nanodrugs　themselves　via　near-infrared　fluorescence　(NIRF)　imaging,　photothermal　imaging,　and　computed　tomography　(CT)　imaging　in　vitro　and　in　vivo.　As　revealed　by　trimodal　imaging,　PCPP　NPs　were　found　to　exhibit　excellent　tumor　accumulation　and　antitumor　efficiency　after　intravenous　injection　into　H22-tumor-bearing　mice.　The　dual-drug　backboned　polyprodrug　nanoplatform　exhibited　great　potential　for　bioimaging　and　combined　chemo-phototherapy.　©　The　Royal　Society　of　Chemistry