This paper describes the powerful practical modification method of elastomers with unsaturated bonds exploiting kinetically stabilized nitrile N-oxides. The stable nitrile N-oxides enable the efficient 1,3-dipolar cycloaddition to both internal olefin and nitrile groups incorporating into versatile elastomers such as acrylonitrile butadiene rubber (NBR), natural rubber (NR), and ethylene-propylene-diene terpolymer (EPDM) to give the corresponding hetero aromatics-containing polymers. The reaction features i) catalyst-free procedure, ii) versatile applicability to various elastomers, iii) high yield, iv) high regio-selectivity, v) no by-product, and vi) remarkable acceleration of reaction rate under solvent-free condition. The scope and limitation of the modification reaction are discussed in detail.