Abstract: The finite element method (FEM) is a widely accepted prediction tool for the steady-state dynamic response analysis of coupled structural-acoustic (SA) systems. However, it is limited to the low frequency range d ue to the fast growing model size for increasing frequencies. An alternative method is the wave based method (WBM) based on the indirect Trefftz method. However, the applicability of the WBM is limited since the high h computational efficiency only appears for moderate geometrical complexity. In order to take advantage of the wide application range of the FEM and the high convergence rate of the WBM, a hybrid method of the two is p roposed. The basic idea is to replace parts of the FE model with simple geometrical shapes by much smaller wave models. The resulting hybrid model has fewer degrees of freedom. The theoretical background of both the FE M and the WBM is briefly discussed, followed by the mathematical description of the hybrid FE-WB method. The hybrid modeling concept is demonstrated for a structural-acoustic system. The results are shown to be in good agreement with numerical simulation results. The example illustrates that the hybrid FE-WB method has the potential to cover the mid-frequency range.