The tapered-plate energy absorber (TPEA) has been accepted as an effective energy dissipator to absorb earthquake-induced energy and improve seismic resistance of a structure. Previous analytical studies associated with the TPEA device were primarily based on simple methods to predict its behavior. In this study, a more complex model, based on plasticity theory, and a finite-element formulation for the TPEA device are developed. The proposed model predicts effectively the device behavior under wind and earthquake loadings. Analytical results obtained by the proposed model are in good agreement with the experimental observations from the tests of the TPEA devices. Furthermore, numerical simulations of a 10-story building equipped with TPEA devices and subjected to earthquake ground motions show that the energy-dissipation capacity of the structure increases, and that its responses to earthquake loadings are significantly reduced when the TPEA devices are employed.