Due to the high magnitude of earthquakes and the poor quality of buildings, Ecuador's seismic risk requires the application of advanced experimental and computational analysis for seismic assessment. This study examines an existing 8-story reinforced concrete moment-resisting frame building, which represents Ecuador's most prevalent structural system. The research focuses on integrating environmental vibration tests and analytical modeling for performance-based seismic assessment, considering three performance objectives. The instrumentation uses six acceleration sensors to conduct environmental vibration tests. For analytical modeling, a nonlinear static analysis is employed using a fiber-based computational tool. The importance of integrating experimental studies to enhance building safety analytical assessments is highlighted, as it provides more realistic data to support predictive modeling. The results show that the building meets the two higher performance objectives; however, further actions are required to meet the lower one.