Purpose <p>A novel energy-based approach for determining the optimum parameters of tuned mass dampers (TMDs) in systems subjected to base excitation is presented.</p> Methods <p>The optimum TMD parameters are determined by minimizing the H-infinity norm of the transfer function associated with the energy response of the main structure, which is assumed to be a single-degree-of-freedom (SDOF) system under harmonic base acceleration. The explicit formulas for the optimal parameters (i.e., tuning frequency and damping ratio of the TMD) are then derived from a nonlinear curve-fitting procedure. The effect of uncertainties in the TMD and structural parameters that can lead to the detuned TMD is also investigated.</p> Results <p>The energy-based optimal TMD successfully minimizes the energy dissipated in the main structure. Additionally, it is highly effective in reducing other response parameters of the main structure, such as its displacement and acceleration. The efficiency of using the proposed TMD parameters for seismic response control of several SDOF and multistory building structures under simulated and real ground motions is demonstrated.</p> Conclusion <p>A significant reduction in the seismic responses of the analyzed structures is observed when the proposed energy-based parameters are used for TMD design, which can be attributed to both the decrease in energy input to the system and the increase in energy dissipated by the TMD.</p>