Magnetite‐based nanozymes have attracted great interest for catalytic cancer therapy enabled by catalyzing hydrogen peroxide (H2O2) to produce highly toxic hydroxyl radicals (•OH) to kill tumor cells. However, their therapeutic efficacies remain low due to insufficient •OH. Here, we report a light‐responsive carbon‐encapsulated magnetite nanodoughnuts (CEMNDs) with dual‐catalytic activities for photothermal‐enhanced chemodynamic therapy (CDT). The CEMNDs can accumulate in tumor and get into tumor cells and effectively act as peroxidase to convert H2O2 to hydroxyl radicals (•OH) that cause tumor cell death. The CEMNDs also possess intrinsic glutathione oxidase‐like activity that which catalyzes the oxidation of reduced glutathione and produce lipid peroxidase for enhanced catalytic therapy. Furthermore, the CEMNDs can absorb 1064 nm light to elevate local temperature and increase release of Fe ions for photothermal therapy (PTT) and enhanced CDT respectively. Our in vivo experiments in an aggressive and drug‐resistant metastatic mouse model of triple negative breast cancer (TNBC) model demonstrate excellent synergistic anti‐tumor function and no measurable systemic toxicity of CEMNDs.This article is protected by copyright. All rights reserved