A three dimensional micromechanically motivated model is proposed here based on firm thermodynamics principles to capture the nonlinear dissipative effects in the polycrystal ferroelectrics. The constraint imposed by the surrounding grains on a subgrain at its boundary during domain switching is modeled by a suitable modification of the switching threshold in a subgrain. The effect of this modification in the dissipation threshold is studied in the polycrystal behavior after due correlation of the subgrain behavior with the single crystal experimental results found in literature. Taking into consideration, all the domain switching possibilities, the volume fractions of each of the variants in a sub-grain is tracked and homogenized for polycrystal behavior. The results show appreciable improvement in modeling the response of the polycrystal ferroelectrics under electromechanical loading conditions. Copyright © 2008 Tech Science Press.