<p>This research investigates the behavior of a flat steel shear wall (FSSWs) system stiffened with vertical trapezoidal corrugated plates in two locations. For this purpose, a one-span, three-story flat steel shear wall that had been previously tested was validated in ABAQUS software. Subsequently, it was stiffened with corrugated plates equal to 50% of the width of the frame panel. The study’s findings demonstrated that initial stiffness, energy absorption, and maximum strength increase when corrugated plates are stiffened. The outcomes also displayed that increasing the thickness of the stiffening corrugated plate increases the parameters mentioned above. The results obtained from this research also showed that, in general, stiffening the flat wall with a corrugated plate in the middle led to a greater increase in maximum resistance compared to the side case. The lateral behavior of the stiffened FSSWs is also influenced by the corrugation angle of the stiffening corrugated plates.</p>