Immobilized nanomaterials have emerged as a transformative class of materials for environmental remediation, offering enhanced stability, reusability, and multifunctionality compared with free nanoparticles. This chapter provides a comprehensive overview of recent advances in the synthesis, structural design, and application of immobilized nanomaterials in thin films for wastewater treatment, air purification, soil remediation, and environmental sensing. The discussion highlights the influence of fabrication methods—ranging from bottom-up nanoparticle synthesis to top-down deposition techniques such as electron beam physical vapor deposition and layer-by-layer assembly—on interfacial properties, surface morphology, and catalytic performance. Comparative analyses between dispersed nanoparticles and immobilized systems reveal that thin-film architectures offer superior mechanical integrity, optical uniformity, and scalability, facilitating integration into industrial reactors and sensing devices. The chapter also examines sustainability considerations, including green synthesis, biopolymer integration, and strategies to mitigate nanoparticle leaching and ecotoxicity. Emerging directions focus on multifunctional hybrid composites that combine adsorption, photocatalysis, and biological degradation, as well as the integration of immobilized systems with smart sensors and Internet of Things (IoT) platforms for real-time monitoring. Although challenges related to scalability, cost, and regulation remain, ongoing advances in materials science and nanotechnology are paving the way for the development of adaptive, sustainable, and intelligent thin-film systems capable of transforming environmental remediation practices at both industrial and global levels.