The consequences of antibiotic misuse, leading to the proliferation of drug-resistant bacteria, present a significant challenge to the field of medicine. Natural compounds such as epigallocatechin gallate (EGCG), derived from green tea, exhibit potent anti-tumor and antibacterial properties. However, the adaptability of tumors to chemotherapy due to their acidic pH and elevated levels of glutathione (GSH), coupled with the challenges posed by postoperative drug-resistant bacterial infections, hinders treatment outcomes. This study successfully synthesized a self-assembling nanocomposite, Cu-EGCG. Leveraging chemodynamic therapy (CDT), photothermal therapy (PTT), and photodynamic therapy (PDT), Cu-EGCG demonstrated robust anti-tumor and antibacterial effects. Additionally, Cu-EGCG exhibited excellent photothermal conversion under 808 nm near-infrared (NIR) radiation, generating singlet oxygen (1O2) upon laser irradiation. In murine tumor and wound models, Cu-EGCG consistently displayed significant anti-tumor and antibacterial efficacy. Display omitted Chemotherapy and surgery stand as primary cancer treatments, yet the unique traits of the tumor microenvironment hinder their effectiveness. The natural compound epigallocatechin gallate (EGCG) possesses potent anti-tumor and antibacterial traits. However, the tumor’s adaptability to chemotherapy due to its acidic pH and elevated glutathione (GSH) levels, coupled with the challenges posed by drug-resistant bacterial infections post-surgery, impede treatment outcomes. To address these challenges, researchers strive to explore innovative treatment strategies, such as multimodal combination therapy. This study successfully synthesized Cu-EGCG, a metal-polyphenol network, and detailly characterized it by using synchrotron radiation and high-resolution mass spectrometry (HRMS). Through chemodynamic therapy (CDT), photothermal therapy (PTT), and photodynamic therapy (PDT), Cu-EGCG showed robust antitumor and antibacterial effects. Cu+ in Cu-EGCG actively participates in a Fenton-like reaction, generating hydroxyl radicals (·OH) upon exposure to hydrogen peroxide (H2O2) and converting to Cu2+. This Cu2+ interacts with GSH, weakening the oxidative stress response of bacteria and tumor cells. Density functional theory (DFT) calculations verified Cu-EGCG’s efficient GSH consumption during its reaction with GSH. Additionally, Cu-EGCG exhibited outstanding photothermal conversion when exposed to 808 nm near-infrared (NIR) radiation and produced singlet oxygen (1O2) upon laser irradiation. In both mouse tumor and wound models, Cu-EGCG showcased remarkable antitumor and antibacterial properties.