In this study, the effects of an energy dissipation device in a reinforced concrete building are presented. The damper that is used in this study is part of the passive energy dissipation systems and absorbs the seismic energy through yielding in bending and frictional forces that occur in the metallic elements of the damper. The existence of this friction-yield damper: (i) increases the stiffness of the structure, (ii) absorbs seismic energy, (iii) and controls the axial forces occurring at the diagonal steel braces. The first step of this study is to present the dynamic response of this damper, testing it experimentally under cyclic loading. These experimental results have been compared to the finite element model of the damper results. In addition, a three-story reinforced concrete building is studied in this paper. It is being analysed using push-over and time history analysis, as regards three different cases, (i) the benchmark r/c building (BM3), (ii) the strengthening building with steel diagonal braces (DS3), and (iii) the strengthening building with the investigated damper (DS3-Damper). A comparison of the strengthening solution is presented and further useful results are observed.