<p>This Special Issue reprint Advanced Polymer Nanocomposites II addresses high-quality original and review papers focused on the scientific discussion and practical application in the field of functional polymer nanocomposites including: (a) optoelectronic materials (papers 1-9); (b) biomedical materials (papers 10-14); and (c) other functional polymer nanocomposites (papers 15-23). We hope that this Special Issue reprint can promote academic research exchanges and identify and respond to tremendous challenges of research in this burgeoning field.</p>