Multifunctional　nanoplatforms　with　integrated　diagnostic　and　therapeutic　functions　have　attracted　tremendous　attention.　Especially,　the　second　near-infrared　(NIR-II)　light　response-based　nanoplatforms　hold　great　potential　in　cancer　theranostic　applications,　which　is　because　the　NIR-II　window　provides　larger　tissue　penetration　depth　and　higher　maximum　permissible　exposure　(MPE)　than　that　of　the　well-studied　first　near-infrared　(NIR-I)　window.　Herein,　we　for　the　first　time　present　a　two-dimensional　(2D)-nanoplatform　based　on　Cu　2　MnS　2　nanoplates　(NPs)　for　magnetic　resonance　imaging　(MRI)/multispectral　optoacoustic　tomography　(MSOT)　dual-modal　imaging-guided　photothermal　therapy　(PTT)　of　cancer　in　the　NIR-II　window.　Methods:　Cu　2　MnS　2　NPs　were　synthesized　through　a　facile　and　environmentally　friendly　process.　A　series　of　experiments,　including　the　characterization　of　Cu　2　MnS　2　NPs,　the　long-term　toxicity　of　Cu　2　MnS　2　NPs　in　BALB/c　nude　mice,　the　applications　of　Cu　2　MnS　2　NPs　for　in　vitro　and　in　vivo　MRI/MSOT　dual-modal　imaging　and　NIR-II　PTT　of　cancer　were　carried　out.　Results:　The　as-synthesized　Cu　2　MnS　2　NPs　exhibit　low　cytotoxicity,　excellent　biocompatibility　as　well　as　high　photothermal　conversion　efficiency　(~49.38%)　and　outstanding　photostability.　Together　with　their　good　T1-shortening　effect　and　strong　absorbance　in　the　NIR-I　and　NIR-II　region,　the　Cu　2　MnS　2　NPs　display　high-contrast　imaging　performance　both　in　MRI　and　MSOT　(900　nm　laser　source).　Moreover,　the　subsequent　in　vitro　and　in　vivo　results　demonstrate　that　the　Cu　2　MnS　2　NPs　possess　excellent　PTT　efficacy　under　1064　nm　laser　irradiation　with　a　low　power　density　(0.6　W　cm　-2　).　In　addition,　the　detailed　long-term　toxicity　studies　further　confirming　the　safety　of　Cu　2　MnS　2　NPs　in　vivo.　Conclusion:　We　have　developed　a　new　2D　Cu　2　MnS　2　NPs　as　multifunctional　theranostic　agents　for　MRI/MSOT　dual-modal　imaging-guided　PTT　of　cancer　in　the　NIR-II　window.　Such　biocompatible　Cu　2　MnS　2　NPs　might　provide　a　new　perspective　for　exploring　new　2D-based　nanoplatforms　with　improved　properties　for　clinical　applications　in　the　future.　©　Ivyspring　International　Publisher.