This chapter gives an overview of polymer-based nanocomposites (PMNC), focusing on the processing. Polymers such as condensation polymers, vinyl polymers, polyolefins, specialty polymers including biodegradable are used in production of PMNC. It is the reinforcement that is in the nanorange size in nanocomposites generally. Reinforcements used are metal powders, silica, clays, and metal oxides. The most important methods of preparing PMNC are intercalation of the polymer or pre-polymer from solution, in-situ intercalative polymerization, melt intercalation, direct mixture of polymer and particulates, template synthesis, in-situ polymerization; and sol-gel process. The structure of polymer-based nanocomposites consists of the matrix material containing the nanosized reinforcement components in the forms of whiskers, particles, nanotubes, fibers, etc. It is clear that polymer-based nanocomposites provide many benefits such as improved properties, minimization of solid wastes films, and lower and improved manufacturing capabilities.