The equations of motion for a viscoelastic polymeric piezoelectric microplate are established based on the thin plate theory and Kelvin–Voigt laws. Polyvinylidene fluoride is chosen as the polymeric piezoelectric material. The plate is assumed to be rectangular and the boundary conditions are clamped at all edges. Liquid is modelled as a damping foundation beneath the plate. The equations are solved using assumed-mode method along with Newmark's β method. The effects of variation in the input voltage, damping coefficient, viscoelastic parameter, and excitation frequency are discussed. The results are compared with the developed finite element method. An excellent agreement is observed between the two methods.