Copper nanowires (CuNWs) are remarkable components that can replace indium tin oxide as transparent electrodes due to their low cost, high conductivity and acceptable transmittance. However, a common coating method can cause poor electrical, optical and adhesive properties because of the creation of loosely connected junctions. In addition, the unsatisfactory thermal and environmental stabilities limit the practical applications. These problems should be overcome in CuNW-based films for reliable transparent electrodes through material and engineering approaches. In this work, a novel transparent composite electrode composed of chitosan and CuNWs on a flexible polyethylene terephthalate (PET) substrate, with synchronously strengthened adhesion, as well as heightened transmittance, reduced resistivity, improved flexibility, enhanced thermal stability and increased environmental stability, was prepared without vacuum processing and high-temperature annealing. The effects of the number of CuNW network layers and chitosan concentration on the performance of chitosan/CuNW composite transparent electrodes were studied. The resulting electrodes exhibitan excellent conductivity (sheet resistance: 15.6 Ω sq-1) and a superior optical transmittance (∼87%) at 550 nm. Calculation of the figure of merit displays a high value of 168, which is the highest among all the reported CuNW-based transparent electrodes. Meanwhile, the sheet resistance did not show great change after 10 tape tests and 10 000 bending cycles, suggesting good adhesion to the PET substrate and outstanding mechanical flexibility. Moreover, the composite transparent electrodes show good stability to resist long-term storage and temperature variation in thermal environment.