Reinforcement corrosion is one of the major factors contributing to reduced seismic capacity and increased vulnerability of reinforced concrete (RC) structures throughout their service life. Nevertheless, the combined effects of seismic design level and corrosion-induced deterioration on the collapse capacity and seismic fragility of these structures have received limited attention. This study aims to evaluate the seismic performance of corrosion-affected RC moment frames designed at different seismic design levels. For this purpose, three 5-, 10-, and 15-story RC moment frames were designed in accordance with conventional seismic design codes for three seismic hazard levels corresponding to 10%, 5%, and 2% probabilities of exceedance in 50 years. Reductions in the mechanical properties of concrete and reinforcing steel, as well as deterioration of the concrete–reinforcement bond due to reinforcement corrosion, were incorporated into the numerical models. The nonlinear behavior of the structures was modeled using OpenSeesPy, and their seismic performance was evaluated through Incremental Dynamic Analysis (IDA) in accordance with the FEMA P-695 methodology using 24 near-field and far-field ground-motion records. Subsequently, seismic fragility curves, median collapse capacity, Collapse Margin Ratio and Adjusted Collapse Margin Ratio (ACMR) were determined for all models. The results showed that increasing the seismic design level shifted the fragility curves toward higher seismic intensity levels and increased the collapse capacity of the structures. Accordingly, the median collapse capacity increased by 58%, 62%, and 120% for the 5-, 10-, and 15-story frames, respectively. Conversely, as the number of stories increased, the median collapse capacity decreased by 51%, 13%, and 32.5% at the 10%, 5%, and 2% seismic design levels, respectively. The findings demonstrate that a higher seismic design level can partially compensate for corrosion-induced performance degradation and improve the seismic reliability of corrosion-affected RC structures.