Piezoelectric materials exhibit nonlinear behavior when subjected to large electric fields. This strong nonlinear material behavior is induced by polarization switching (i.e., change of the polarization direction). In this paper, a nonlinear finite element code for a coupled electro-mechanical problem is presented to model polarization switchings. An isoparametric plane strain four-node element with nodal displacements and voltage as degrees of freedom is used to approximate the geometry. The element incorporates two types of polarization switching: 90° and 180°, where electric flux is used as a switching criterion. Three cases are studied in this paper: a partially electroded specimen simulating 180° polarization switching, a fully electroded specimen simulating 90° switching and a plate containing a void. The analytical results are compared with experimental data obtained from a Moiré interferometer. Comparison between experimental data and theoretical results indicates reasonable agreement between the two suggesting that the correct physics is incorporated in the analytical model.