—In this paper, we extend our previously published hybrid analytical model which is for the estimation of shielding effectiveness of a dual-cavity structure with an aperture array to generalize the model for a wider range of applications. In the proposed model, the aperture array in the center, off-center, higher-order modes, and multi-cavity structure are taken into consideration, respectively. At last, a comparison of the results calculated by the extended hybrid analytical model with those obtained by the simulation software CST is given. The results show that the extended hybrid analytical model for the shielding effectiveness prediction of a three-cavity structure with numerous apertures has a higher precision and a higher efficiency. © 2020, Electromagnetics Academy. All rights reserved.