This paper deals with the vibro-acoustic coupling of an irregular enclosure covered with a PZT-bonded panel. The modeling of the system is developed with full consideration of the acoustic-structural-piezoelectric interactions between the actuated panel and the enclosure, along with the modeling of the irregular shape of the enclosure. Simulations are conducted to investigate the effect of the actuation patch on structural modal modification, and subsequently on the structural-acoustic coupling mechanism. Results show that the structural mode shapes can be altered significantly, depending on the patch locations and structural frequency behavior (singlet, doublet or closely coupled), and the patch effect on the coupling density is noticeable, especially when the inclined angle of the enclosure is within a sensitive region. This study provides a more thorough physical understanding of how the PZT patch influences the modal coupling between the actuated panel and the enclosure, which might be useful for all control techniques involving PZT actuated panels.