The control of the nanostructure and the addition of nanoparticles to polymers have led to structural and functional property enhancements in a number of polymeric systems as a material answer to continuous requirements from advanced industrial sectors. The availability of new nanoparticles with extraordinary properties (i.e. carbon nanotubes, graphenes, but also nanoclays, nanocellulose, metals and ceramics) have determined new and exciting possibilities for a continuous enlargement of polymer markets. However, the potentialities of these new materials are still strongly dependent on the development and scaling-up of reliable processing routes. Therefore, the purpose of this report is to review the main processing approaches for nanostructured polymers and nanocomposites starting with a brief review of available nanoparticles and on their functionalization to promote a better polymer–particle interaction. Regarding processing, the review firstly addresses the bottom-up approaches typically adopted for nanostructured polymers, blends and copolymers. Then, the different technologies required by the top-down processing of thermoplastic and thermosetting polymer matrix systems are reviewed. Finally, the report addresses the recent applications of nanostructured polymers and nanocomposites as matrices of advanced composite materials. In all cases, the main processing approaches and the main structural and functional properties characterizing these materials and their potential and current industrial applications are specifically addressed.