The seismic performance of existing buildings can be significantly affected by damage accumulation over time. This study focuses on a reinforced concrete (RC) building archetype representative of buildings designed for gravity loads only in the 1950s, subjected to both rebar corrosion and differential soil settlements. The building structure consists of unidirectional frames and one-way joist slabs according to design codes in force at the time of construction and associated engineering practice. A fiber-based modeling approach is used to capture the nonlinear behavior of materials and to simulate progressive effects of deterioration and deformations, or even damage, due to soil settlements under earthquake loading. Corrosion-related degradation of reinforcing steel is simulated through increasing levels of loss of material properties in the bare RC frame model. Afterwards, the structural model is first subjected to increasing levels of soil settlements, then performing nonlinear static analysis to investigate the impact on seismic capacity. Analysis results support multi-hazard assessment of existing RC buildings under material degradation, soil settlements and seismic actions.