From the above mentioned, the acrylate-based nanocomposites were prepared in this research work by adding the nano-ZnO into the poly(methyl methacrylate-co-butyl acrylate) matrix (P(MMA-co-BA)). It is known that the presence of ZnO nanoparticles is expected to enhance not only the mechanical properties of nanocomposites, but also thermal stability and physical properties. In addition, some superior properties of ZnO, such as antibacterial, anti-static and self-cleaning character, will be effective when ZnO nanoparticles locate on top, rather than, beneath of the polymers’ surfaces. Nevertheless, direct coating of ZnO nanoparticles on the surfaces of acrylate copolymers is not a good choice because their polarity mismatches lead to weak interfacial adhesion between the coating nanoparticles and the polymer substrate. To overcome this weak point, this research performed the hydrothermal treatment of nano-ZnO/P(MMA-co-BA) nanocomposites in ammonium hydroxide solution using various pH and treatment time. The nano-ZnO embedded in the matrix could act as the seeds for hydrothermal growth of ZnO nanostructures and effectively immobilize these newly formed ZnO on the surfaces of polymer nanocomposites. In addition, the hydrothermal treatment is a green chemistry due to its simple process, using low concentration of non-toxic chemical reagents and low treatment temperature.