This paper introduces three wavelet-based damage-sensitive features (DSFs) extracted from structural responses recorded during earthquakes to diagnose structural damage. Because earthquake excitations are nonstationary, the wavelet transform, which represents data as a weighted sum of time-localized waves, is used to model the structural responses. These DSFs are defined as functions of wavelet energies at particular frequencies and specific times. The first DSF (DSF 1) indicates how the wavelet energy at the original natural frequency of the structure changes as the damage progresses. The second DSF (DSF 2) indicates how much the wavelet energy is spread out in time. The third DSF (DSF 3) reflects how slowly the wavelet energy decays with time. The performance of these DSFs is validated using two sets of shake-table test data. The results show that as the damage extent increases, the DSF 1 value decreases and the DSF 2 and DSF 3 values increase. Thus, these DSFs can be used to diagnose structural damage. The robustness of these DSFs to different input ground motions is also investigated using a set of simulated data. © 2011 American Society of Civil Engineers.