A submerged flexible plate with piezoelectric layers bonded to both faces of it may work as a piezoelectric wave energy converter (PWEC), the elastic motion of which excited by water waves can be transformed into useful electricity due to the piezoelectric effect. In this paper, wave power extraction from a PWEC moored in front of a pile-supported breakwater is investigated. The PWEC is simply supported at the edge. To evaluate the performance of the breakwater-attached PWEC, a hydroelastic model with the electro-mechanical and the hydrodynamic problems of the PWEC coupled together is developed based on linear potential flow theory and the eigenfunction matching method. Effects of the width and submergence of the PWEC, and also the width and draft of the breakwater, on wave power absorption of the breakwater integrated PWEC are examined with the employment of the present model. It is revealed that as the PWEC width increases, more peaks of the frequency response of wave power absorption efficiency can be excited in the computed range of wave conditions. As the PWEC submergence increases, the main peaks of the wave power absorption efficiency become lower and narrower, and slightly shift towards large wave frequencies.