The increasing population, limited residential space, and scarcity of suitable land for construction have led to a rise in the construction of high-rise buildings (HRBs) as a means to provide additional housing. The increase in human activities (such as excavations for geothermal resources) has led to an increase in seismic activity, making HRBs more vulnerable to earthquakes. Structural analysis of HRBs that are exposed to seismic loadings depends on one of the most important factors that judge the stability and resistance to seismic waves which is the stiffness of the buildings. Various methods that reduce flexibility and enhance stiffness for HRBs are the subject of this numerical investigation, and they were applied to a high-rise building (HRB) of 20 floors, considering soil–structure interaction (SSI). The stiffening methods adopted herein are steel or concrete shear walls (SWs) in specific arrangements, and different bracings in specific arrangements. Moreover, in this study, tuned mass dampers (TMDs) are used, as a damping method of the HRB seismic response, also considering SSI, and the results are compared with the stiffening methods results to judge how the applied methods enhance the seismic resistance of HRBs. These methods, which were used to influence the stiffness or the damping of the building, had different positive effects on the seismic response of the HRBs, which appeared in the results through the base shears, the base moments, the maximum top displacement, and the fundamental period of the building.