Stretchable electronics have progressed greatly and have found their way into various applications, thus resulting in a growing demand for high-quality stretchable conductors. Poly(dimethylsiloxane) (PDMS) is the mostly frequently exploited elastomeric substrate for the construction of a stretchable and conductive platform because of its valuable features, such as superb stretch ability, high transparency, and reliable biocompatibility. However, the weak adhesion between the PDMS substrate and the conductive components has always been an intractable issue which undermines the good and stable performance of the resultant devices. We proposed a quasi in situ polymerization method to effectively build a tight and stable attachment between copper nanowire (Cu NW) and the PDMS substrate. The Cu NWs/PDMS conductors show excellent conductivity and antioxidation stability (R-0/ < 1.4 for 50 days in air), enhanced interface adhesion, and stretch ability (80% strain, R/R-0 similar to 5), without any complicated preconfiguration of the PDMS substrates. For application demonstration, the Cu NWs/PDMS conductor was deployed as the stretchable electric wiring to illuminate a light-emitting diode. Furthermore, a stretchable capacitive strain sensor was fabricated using the Cu NWs/PDMS as electrodes. The sensor possessed a gauge factor of 0.82 and the minimum detection limit of 1% strain.