<p>Heterostructures are composed of spatially distinct zones with differing mechanical and/or physical properties. When carefully engineered, these architectures can exhibit superior performance compared with their homogeneous counterparts. However, not all heterostructures inherently lead to a pronounced improvement in properties. Realizing the full potential of complex heterostructures requires a rigorous understanding of the structure–property relationships and mechanisms related to inter-zone interactions. This knowledge is essential if the heterostructure effect is to be effectively harnessed and the overall performance of the material optimized. Here we examine the fundamental mechanisms underlying the unusual mechanical properties of heterostructured materials, highlighting the important role of interactive coupling in the heterozone boundary-affected regions. We outline strategies for evaluating the effects that arise from heterostructures, in particular the heterodeformation-induced stress. We also provide guidelines for designing heterostructured materials with optimal mechanical properties, and discuss future directions for property design and characterization development.</p>