Reinforced masonry (RM) shear walls with boundary elements (BE) have been recently presented as a ductile alternative to RM rectangular shear walls. The present study addresses the applicability of reinforcing masonry shear walls with glass fibre-reinforced polymer (GFRP) bars to attain reasonable strength and drift. GFRP-RM shear walls are a corrosion-free lateral resisting system that is transparent to magnetic fields and radio frequencies and nonconductive thermally and electrically. A numerical macro-model is developed using OpenSees to simulate the in-plane response of flexure-dominated reinforced masonry shear walls with boundary elements (RMSW-BE). The model was validated against experimentally tested walls from the literature. The boundary elements were designed with C-shaped masonry blocks. A numerical study is performed on thirty-four flexure-dominated shear walls to evaluate the influence of different design parameters on the inelastic behaviour of RMSW-BEs under quasi-static fully reversed cyclic loading. The investigated parameters are transverse hoop spacing, amount of vertical reinforcement in the boundary element, GFRP or steel reinforcement, and aspect ratio of the wall. In addition, walls with rectangular boundary elements were investigated to study the effect of increasing their size on the overall wall response. The influence of the design parameters on the hysteretic response, stiffness degradation, effective stiffness, and ductility related response modification factor was investigated to evaluate the enhancement in the seismic performance of RM buildings with RMSW-BE.