Three-dimensional (3D)-bioprinted nanozyme-hydrogel composites bridge nanocatalytic therapeutics and biomimetic tumor engineering for advancing tumor modeling and localized cancer treatment. Nanozymes are catalytic nanomaterials that emulate enzyme-mimicking activities while overcoming the instability and high cost of natural enzymes. Since the discovery of Fe3O4 peroxidase (POD)-mimicking catalysis, nanozyme research has advanced from empirical exploration to rational structural engineering for biomedical applications. Compared with conventional delivery vehicles limited by rapid clearance and insufficient tumor accumulation, 3D bioprinting enables precise spatial integration of nanozymes within tunable hydrogel bioinks, offering programmable construction of biomimetic tumor microenvironments (TMEs) and localized therapeutic scaffolds. This review systematically summarizes nanozyme catalytic classification, structural modulation strategies, and biomedical advances, with a core emphasis on state-of-the-art 3D-bioprinted nanozyme–hydrogel composite systems for tumor modeling and cancer therapy. Rationally engineered nanozymes exhibit tunable POD-, oxidase-, catalase-, and superoxide dismutase–mimicking activities, often based on metal-centered electron transfer. Integrated into printable hydrogel matrices, nanozymes achieve sustained intratumoral retention, overcoming the drawbacks of free nanocatalytic agents. 3D bioprinting recapitulates TME heterogeneity by constructing scaffolds with customizable stiffness, redox gradients, and porous architecture, supporting high-fidelity tumor modeling and high-throughput drug screening. In therapeutic applications, printed nanozyme systems remodel immunosuppressive TMEs, trigger tumor ferroptosis and immunogenic cell death via the cGAS-STING pathway, and enable stepwise antitumor cascades to suppress tumor growth, invasion, and recurrence, synergizing with photothermal and sonodynamic therapies. Nevertheless, critical challenges persist, including inherent trade-offs among bioink printability, structural stability, and catalytic performance; insufficient lesion-specific selectivity; and a lack of standardized bioprinting protocols. Optimizing composite formulations and printing parameters will promote the clinical translation of next-generation nanozyme-based tumor theranostic platforms.