The design of lateral-resisting reinforced-concrete elements requires prediction of the fundamental period and drift, which are determined using linear elastic dynamic analysis. To estimate the linear elastic response, the cross section of the structural element is assumed to have a linear flexural stiffness that accounts for cracking. This emphasizes the need for a reliable model for the effective stiffness in both flexure and shear response. In this study, six reinforced concrete (RC) shear walls reinforced entirely with glass fiber-reinforced polymers (GFRPs) reinforced bars were tested under reversed cyclic loading. The wall portion of all the specimens had the same dimensions: 3500 mm (137.8 in.) in height, 1500 mm (59.1 in.) in length, and 200 mm (7.87 in.) in width. The test specimens were subjected to a constant axial load of 0.15fc′Ag and a displacement-controlled lateral-loading history. The experimental results were presented and discussed to introduce the effective stiffness relationship based on cracking, failure progression, deformation, and strength degradation. The deformability factor was estimated using the serviceability and ultimate limit states based on the allowable deformation limits. A simple trilinear moment-curvature model was developed to predict the flexural response of the tested walls. A simple procedure is proposed and recommended to predict the lateral displacement of the GFRP-reinforced shear walls.