<p>Piezoelectric-polymer composites, which integrate piezoelectric ceramic phases with elastic polymer matrices, have emerged as promising materials for applications in smart structures, particularly as sensors and actuators. Their appeal stems from attributes such as low density, high flexibility, robust plasticity, and straightforward performance tunability. The microstructure of these composites, intricately influenced by processing conditions, comprises diverse phases and components with varying compositions and architectures. To harness their full potential, it is imperative to control the evolution of their microstructures and unravel the complex interplay between their structure and properties. This paper reviews key micromechanical models that elucidate the microstructure-property relationship in piezoelectric-polymer composites. Furthermore, it delves into interface theories that explore the influence of surface and interface effects on heterogeneous nanostructured materials. The article also outlines methods for interface design in composite systems, tailored to various filler types and morphologies. Lastly, strategies are proposed to uncover the local structure–property correlations at the interface of piezoelectric-polymer nanocomposites, thereby advancing our comprehension of these advanced materials.</p>