<p>Developing new corrosion-resistant alloys with both excellent mechanical properties and corrosion resistance is crucial for coping with harsh service environments. This study systematically investigates the synergistic effects of multi-scale heterogeneous structures on the mechanical properties and corrosion resistance of the Al₁₇Co_28.6Cr_14.3Fe_14.3Ni_25.8 eutectic high-entropy alloy (EHEA). By cold-rolling the as-cast alloy and recrystallization annealing at different temperatures, a heterogeneous structure composed of refined FCC/B2 lamellae and nanoscale precipitates was successfully formed. The results show that the heterogeneous structure significantly enhances the strength and elongation. The performance optimization is attributed to grain-refinement strengthening, precipitation strengthening, and strain-gradient strengthening induced by the heterogeneous structure. Electrochemical tests indicate that the multi-scale heterogeneous structure also improves the corrosion resistance of EHEA in 3.5% NaCl solution, mainly due to the dispersed nanoscale precipitates, which refine the anodic regions and promote uniform formation and rapid repair of the passive film. However, excessively high recrystallization temperatures lead to the aggregation of fine-grain clusters, thereby decreasing corrosion resistance. This study provides important insights into synergistically optimizing the mechanical and corrosion-resistance properties of high-entropy alloys through microstructural design.</p>