Hybrid composite materials and devices have gained immense research interest in recent years. It is due to their multifunctional properties and application in various fields, especially in energy harvesting. The hybrid composites, smart material layers with multiphysical coupling, are able to convert different types of energy. Therefore, combining smart materials with different coupling properties to design a hybrid composite is an interesting field to study further. This chapter focuses on the hybrid composite composed of shape memory alloys (SMAs) and P(VDF-TrFE) piezoelectric polymer. This composite can convert the widely available waste heat into electric energy. The present chapter presents a finite element analysis of the SMA/piezoelectric composite after describing some available models for the thermomechanical behavior of the SMA, for the electromechanical behavior of the piezoelectric layer, and finally for the hybrid composite multiphysical behaviors. The experimental results show the feasibility of the composite harvester to convert the thermal–mechanical energy into electrical energy. Furthermore, it describes an example of an experimental setup allowing the thermomechanical characterization of the harvester. This allows to measure its electrical response when subjected to periodic heating and cooling. Also, this chapter introduces an integrated converter step-up to efficiently convert the piezoelectric response from the device. Therefore this composite hybrid system opens an opportunity to harvest thermal energy from the ambient environment. This device can power small-scale electronic devices such as sensors, MEMS, or biomedical devices in an autonomous way.