<p>Perovskite–polymer nanocomposites have recently gained significant attention as structurally engineered hybrid systems designed to overcome the intrinsic environmental and mechanical limitations of metal halide perovskites. Rather than relying solely on compositional tuning of the perovskite phase, current research increasingly emphasizes architectural integration, where polymer matrices regulate crystallization, reinforce mechanical integrity, and enhance resistance to moisture and thermal degradation. This review provides a focused analysis of material design principles and structural engineering strategies employed in perovskite–polymer nanocomposites, including in situ polymerization, interfacial passivation, electrospun fiber formation, multilayer encapsulation, and additive manufacturing approaches. The influence of composite morphology and polymer–perovskite interfacial interactions on optoelectronic performance is critically examined.</p><p>Representative applications in flexible photovoltaics, light-emitting systems, wearable sensors, and fiber-based optoelectronic platforms are discussed with emphasis on performance enhancement mechanisms and stability improvements. Key challenges associated with long-term operational durability, scalable fabrication, and environmental sustainability are analyzed, and emerging directions such as lead-reduced compositions, recyclable polymers, and multifunctional textile-integrated devices are outlined. By positioning polymer incorporation as a structural and interfacial engineering strategy rather than a simple encapsulation approach, this review establishes a materials-driven framework for the development of mechanically robust and application-ready perovskite-based optoelectronic systems.</p>