Nanopolymers represent one of the most dynamic areas of nanotechnology, offering new opportunities to advance biomedical science and healthcare. This chapter explores the fundamental principles, design strategies, and wide-ranging applications of nanopolymeric systems in medicine. In particular, the chapter explores their applications in drug and gene delivery, diagnostics, medical imaging, vaccine development, cellular regulation and biosensing. Due to their compatibility with biological systems, tunable surface chemistry, and responsiveness to various stimuli, polymer-based nanomaterials possess unique characteristics that facilitate precise targeting, regulated release, and multifunctional activity. These characteristics have been key to progressing both therapeutic and diagnostic methods. Case studies highlight applications in cancer treatment, cardiovascular and metabolic disorders, infectious diseases, and neurodegenerative conditions, illustrating their translational promise. The chapter also discusses emerging multimodal and theranostic approaches that integrate treatment with real-time monitoring. Finally, the challenges of clinical implementation, including toxicity, immunogenicity, large scale production, and regulatory considerations, are addressed along with perspectives on future directions. By bridging nanoscale science with biomedical needs, nanopolymers are poised to play a pivotal role in shaping the future of precision medicine and next generation healthcare.