The mobility power flow (MPF) approach is used in this paper to describe the flexural behavior of an L‐shaped plate structure consisting of thick plates with rotary inertia and shear deformation effects included in the analysis. The introduction of the thick plate effects significantly increases the complexity of the structural mobility functions used in the definitions of the power flow terms; however, because of the substructuring that is used in the MPF approach, the complexity of the problem is significantly reduced as compared to solving for the global structure. Additionally, with the MPF approach the modal behavior is described. The MPF analysis of the L‐shaped plate is performed for the case of point force excitation on one plate, with the two plates being identical in both size and thickness. The results of this analysis are compared to results from the finite‐element analysis (FEA) and the statistical energy analysis (SEA) and show very good agreement in the low‐ and high‐frequency regimes, respectively.