Plastic wastes have posed serious environmental and health issues. Recycling plastic wastes to produce value-added products, however, still remains challenging. Herein, porous nanocomposites derived from polyethylene film wastes were fabricated via thermally induced phase separation method, in which they were employed as supported substrates to self-assemble functional components into multifunctional materials with unique property profiles. The resulting polymeric porous nanocomposites consisting of hybrid nanoparticles and flexible polyethylene bulk not only provided excellent UV resistance, but also ensured superior mechanical robustness against external decomposition and injuries. Specific properties and functionalities, including the sequential combination of functional ink and superhydrophobic layer, were successfully incorporated into the porous nanocomposites by altering functional components. The self-assembly properties of these final multifunctional materials were demonstrated by different performance tests, such as indicating temperature, conductive electrode, superhydrophobic layer. It is found that our fabrication methodology holds great potential for efficient recovery of polyethylene film wastes toward advancing sustainability goals. Furthermore, the proposed self-assembly strategy provides a promising route to develop multifunctional materials with tunable functions and high performance for future designing of smart materials.