The subject of this study is the investigation of historical masonry buildings under earthquake loads. During any earthquake the behaviour of the structural system of masonry buildings is very complicated, and the shear resistances are very low. The masonry building's wall materials, thickness, height and workmanship have a significant affect on the stability and shear resistance of the buildings. The dimensions of wall openings for windows and doors and their placing in the wall, and continuous walls or non continuous walls are also important for stability. In order to prepare a weak masonry building for a possible and heavily damaging earthquake, the structural system needs strengthening to increase its seismic performance. In this study, in order to strengthen masonry buildings, two different strengthening structural models are considered. Firstly, the masonry building is strengthened with the additional RC shear walls, secondly; the walls of the masonry building are strengthened with the FRP/GFRP grid bonded. For example, an existing and historical masonry building chosen from Istanbul is considered. Their structural systems, with strengthened and non strengthened examples, are analyzed under earthquake loads. The results of the analyses are investigated and the obtained seismic performances of the different strengthened structural systems are compared between each other. Consequently, seismic performance and lateral displacements are improved by strengthening with additional RC shear walls and/or FRP/GFRP grid bonded systems. The analyses also show the displacements of the strengthened systems are reduced and these are improved 9 and 4 times according to the present building, respectively. Finally, to maintain outdoor views and for easy application, the FRP/GFRP grid bonded strengthened systems are recommended instead of the additional RC shear wall system.