<p>Steel shear wall systems have become increasingly prevalent in modern building design as effective elements for resisting lateral loads. Concurrently, reinforced concrete shear walls have been extensively utilized owing to their substantial stiffness and load-resisting capability. Despite their widespread application and advantages, both systems exhibit inherent performance limitations. Reinforced concrete shear walls are vulnerable to tensile cracking in regions subjected to tension, whereas steel shear walls are prone to out-of-plane buckling of the infill steel plate under compressive stresses. Such buckling behavior adversely affects shear stiffness, load-carrying capacity, and energy dissipation performance. Composite steel plate shear walls (CSPSWs) have been developed to overcome these deficiencies by combining the advantageous properties of steel and concrete systems. A typical CSPSW configuration consists of boundary frame components and a steel infill plate that is laterally restrained by reinforced concrete panels attached to one or both sides. In most existing implementations, conventional reinforced concrete serves as the restraining material. The present study evaluates and compares the structural performance of CSPSWs employing conventional reinforced concrete with those incorporating Engineered Cementitious Composite (ECC). The shear behavior of CSPSWs subjected to pure shear loading is investigated through a combination of analytical modeling and numerical simulation. An analytical formulation is proposed to predict the ultimate shear strength of CSPSWs and is subsequently validated using finite element analysis. The comparison demonstrates good agreement between the analytical predictions and numerical results, confirming the reliability of the proposed model. Additionally, the results indicate that the use of ECC as a restraining material leads to significant enhancements in both ultimate shear capacity and ductility when compared to conventional reinforced concrete.</p>