Immobilized metal affinity (IMA) magnetic adsorbents exhibit an exciting preference for histidine (His)-rich proteins, whereas their application was limited due to the leaching of copper ions and poor dispersibility, greatly influencing their sustainability and adsorption performance. Herein, we propose a novel IMA adsorbent based on montmorillonite (MMT)-supported, copper-doped magnetic nanoparticles (Fe3O4−Cu/MMT) for highly specific recognition and separation of His-rich proteins. In the process, Fe3O4−Cu/MMT nanomaterials were synthesized by a one-step solvothermal method. The obtained adsorbents exhibit enhanced adsorption capacity (758.7 mg g–1) and selectivity (SF < 0.2) toward bovine hemoglobin (BHb) as a model derived from good dispersity, making more anchor sites exposed. Also, the adsorbent can be facilely regenerated with negligible leakage of copper ions and no need for re-incubation in a metal salt solution, maintaining high performance for six cycles. Furthermore, bovine blood was opted as a realistic specimen for evaluating the adsorption capability of the proposed adsorbent, emphasizing its good practicality for His-rich protein separation.