A numerical study is carried out to understand adhesive layer effects on the electromechanical coupling of piezoelectric sensors bonded to structures. This study shows that electrical signatures depend on the bonding conditions along the interface structure/adhesive/sensor. A mathematical model for electrical signatures was established using the Maxwell’s equation (Gauss law for electricity). The mechanical analysis was defined considering only shear deformation along the adhesive layer. Numerical solutions were obtained by the finite element method and compared with analytical solutions. The analytical solution was provided by solving differential equations in terms of displacements. Results indicate that the thickness and length of the adhesive layer have significant effects on electrical signatures and these effects can be applied to detect debonding of piezoelectric sensors.