Abstract: The development of high-performance functional composites has become a research hotspot in response to the hazards of overheating and electromagnetic radiation in modern electronic devices. Herein, we grew magnetic Fe₃O₄ particles in situ on the MXene layer to obtain an MXene@Fe₃O₄ composite with rich heterogeneous interfaces. Owing to the unique heterostructure and the synergistic effects of multiple electromagnetic wave absorption mechanisms, the composite achieved a minimum reflection loss of −27.14 dB and an effective absorption bandwidth of 2.05 GHz at an absorption thickness of 2 mm. Moreover, the MXene@Fe₃O₄ composite could be encapsulated in thermoplastic polyurethane (TPU) via thermal curing. The obtained composite elastomer exhibited a strong tensile strength, and its thermal diffusivity was 113% higher than that of pure TPU. Such additional mechanical properties and thermal conduction features render this composite elastomer an advanced electromagnetic absorber to adapt to the ever-changing environment for expanding practical applications.