Herein, PPy@MnO₂ nanocomposites were first harvested by anchoring MnO₂ nanosheets on polypyrrole (PPy) nanoparticles via an in situ redox reaction, then polyethylene glycol (PEG) modifier and methylene blue (MB) photosensitizer were linked through electrostatic interactions to obtain PPy@MnO₂-PEG-MB nanoarchitectures. PPy nanoparticles ensure photothermal therapy (PTT) ability and MnO₂ nanosheets ameliorate tumor hypoxia for enhanced photodynamic therapy (PDT). Therefore, a multifunctional nanotherapeutic system was constructed for the combined PTT/PDT of tumors. For extracellular photothermal properties, the optimal temperature elevation was 52.6 °C with 54.4% photothermal conversion efficiency. The extracellular PDT ability was measured by detecting ¹O₂ generation; more ¹O₂ was produced under acidic conditions in the presence of H₂O₂ (a simulated tumor microenvironment). The effective cellular uptake of the nanotherapeutic system in HeLa cells was observed by confocal laser scanning microscopy (CLSM). CLSM also indicated that more ¹O₂ was generated by the nanotherapeutic system as compared to free MB in HeLa cells, confirming the amelioration of tumor hypoxia by MnO₂ nanosheets. MTT assays demonstrated that the nanotherapeutic system possessed superior biocompatibility without laser irradiation, and the lowest cell viabilities for single PTT and PDT groups were 13.78%, 38.82% respectively, while there was only 1.29% cell viability in the combined PTT and PDT group. These results suggest that the strategy of assembling PPy with MnO₂ for a multifunctional PTT and enhanced PDT nanoplatform was realized, and opens up an unimpeded approach for integrating photothermal reduction materials with MnO₂ for use in synergistic PTT and PDT.