Abstract: The development of 3D structural composites with electromagnetic (EM) wave absorption could attenuate EM waves. Herein, magnetized flower-like Cu₉S₅/ZnFe₂O₄ composites were fabricated through a multistep hydrothermal method. The crystallographic and surface phase chemical information, morphological structure, and magnetic and EM parameters of the composites were analyzed. The prepared Cu₉S₅/ZnFe₂O₄ composites have multiple loss paths for EM waves and present an overall 3D flower-like structure. The Cu₉S₅/ZnFe₂O₄ composites exhibit a minimum reflection loss of −54.38 dB and a broad effective absorption bandwidth of 5.92 GHz. Through magnetization, ZnFe₂O₄ particles are self-assembled and grown on the surfaces of Cu₉S₅. Such a modification is conducive to the generation of additional cross-linking contact sites and the effective introduction of a large number of phase interfaces, crystalline defects, special three-dimensional flower-like structures, and magneto–electrical coupling loss effects. Moreover, the synergistic effect of multiple loss strategies effectively improves EM wave absorption by the material. This work can provide a strategy for the use of magnetization-modified sulfide composite functional materials in EM wave absorption.