This chapter provides an overview of the recent progress regarding click polymerizations using nitrile N-oxides applicable to various dipolarophiles. The pronounced reactivity of nitrile N-oxides enables metal (or catalyst)-free 1,3-dipolar cycloadditions with unsaturated bond-containing compounds such as alkynes, alkenes, and nitriles, indicating high potential in the synthesis of a variety of macromolecules and supramolecules via “click” molecular integration. For this purpose, kinetically stabilized nitrile N-oxides play a particularly important role. The first part of this chapter deals with the general topics of nitrile N-oxides, i.e. chemistry, synthetic methods, and reactions. The main discussion is divided into two parts: one is devoted to aromatic nitrile N-oxides, and the other is on aliphatic nitrile N-oxides, because these nitrile N-oxides have somewhat different features in terms of synthesis and reactivity. One of the most attractive features of nitrile N-oxides is that they undergo efficient cycloaddition under solvent-free conditions. Considering these features, it is obvious that nitrile N-oxides have very high potential to open a new world of click reactions and polymerizations. The number of publications mainly on polymerization using nitrile N-oxides is cited at the end of this chapter.