One of the fundamental challenges in structural design and evaluation is the performance of structures under seismic conditions, particularly under repeated and sequential earthquakes. Natural earthquakes do not usually occur as single events; rather, in most cases, aftershocks and sometimes other earthquakes also occur within a short time interval. Therefore, the present research aims to investigate the performance of reinforced concrete frame systems under repeated and sequential earthquake loads. In this study, structural frames were subjected to uniform loading (to examine the system response to continuous loads) and cyclic loading (to investigate the system behavior under variable and periodic loads). In this research, seven real sequential seismic records obtained from the PEER database were used to evaluate the seismic behavior of structures under sequential earthquakes. Two reinforced concrete buildings, four-story and eight-story, with medium ductility, designed based on modern performance-based design methods, were considered. The results showed that in the four-story regular and irregular concrete structures, the Park and Ang damage index, the maximum lateral displacement of the stories, and the maximum story drift ratio under sequential seismic loading, compared to main shocks and aftershocks, were significantly increased. In some seismic records, this increase reached approximately two times. Also, in comparison, the mentioned instantaneous parameters in the irregular building were higher than in the regular building. In the eight-story regular and irregular concrete structures, it was observed that the Park and Ang damage index, both locally and globally, under sequential earthquakes, compared to main shocks and aftershocks, had higher values. However, it did not exceed the critical value (1).