The integration of nanotechnology with polymer science has led to the development of nanopolymers, materials that exhibit novel properties distinct from their bulk counterparts. Among the key parameters influencing their behavior, the nanoscale size and shape play a pivotal role in determining their physicochemical and functional performance. Therefore, this chapter provides a comprehensive understanding on quantum confinement effects, increased surface-to-volume ratio, and shape-induced anisotropy and how these phenomena can be harnessed to tailor nanopolymer performance for specific applications. Further, the effect of size and shape tuning and their impact on mechanical, optical, thermal, electrical, surface and functional properties of nanopolymers are emphasized. Additionally, the chapter outlines the synthesis strategies to precisely control these parameters, and highlights their relevance with particular focus on biomedical, sensing, coating and energy storage applications.