The incorporation of zinc oxide (ZnO) nanoparticles into polymeric membranes has emerged as a promising strategy to address the limitations of conventional membrane systems in separation, filtration, and biomedical applications. This chapter presents an overview of nano ZnO-blended polymeric membranes, describing their synthesis methodologies, structural and morphological characteristics, physicochemical properties, and various applications. This chapter focuses on the role of ZnO nanoparticles in enhancing membrane performance, including improved hydrophilicity, mechanical reinforcement thermal and UV stability, as well as significant antimicrobial and photocatalytic functionalities. Fabrication techniques such as solution casting, phase inversion, electrospinning, in situ polymerization, and sol-gel synthesis are discussed. The applications including wastewater treatment, biomedical engineering (e.g., wound dressings, drug delivery systems), environmental remediation, food packaging, and protective coatings are also discussed. The chapter also addresses current challenges related to nanoparticle agglomeration, scalability, and long-term stability and suggests future directions for the development of next-generation multifunctional membrane materials.