Hysteretic nonlinearities significantly affect the behavior of devices based on piezoelectric materials. The topic has been widely addressed in the actuation framework, as modeling nonlinear effects is crucial for the dynamic control of piezoelectric actuators. Far less studies, however, discuss the role of hysteresis in the dynamic response of piezoelectric energy harvesters, usually adopting phenomenological modeling approaches. In this work, a physics-based model is employed to reproduce-through a probabilistic thermodynamic approach-the process behind hysteresis in piezoceramic transducers, i.e., the switching of dipoles in crystal domains. A multi-scale approach is then adopted in order to comprise hysteretic effects in the dynamic response of a piezoelectric energy harvester, modeled as a SDOF system. Effects of hysteretic nonlinearities on the device behavior are investigated by means of simulations, and a detailed discussion on the role of material parameters is reported. Moreover, a comparison between predictions of two models-with and without hysteresis-is presented.