Flexible all-solid-state energy storage devices that can function under considerably large mechanical deformation have shown great promise for portable electronics applications. However, conventional techniques are cumbersome in building cost-effective flexible all-solid-state energy storage devices, thus limiting their widespread applications. Here we report a flexible all-solid-state supercapacitor whose electrodes were prepared via a facile oxidation-assisted dealloying protocol for the first time. The electrodes demonstrate good flexibility and excellent performance. We assembled a prototype all-solid-state asymmetric supercapacitor (ASC) from the asprepared Co3O4 flakes and gamma-Fe2O3 nanoparticles as the positive and negative electrodes, respectively. The flexible ASC device possesses an extended operating voltage window of 1.7 V and a high energy density of 38.1 Wh/kg. We also demonstrated that four supercapacitor cells that were constructed in series illuminated 52 LEDs for at least 7 min. The ASC device has excellent power density and energy density that comparable to the art-of-the-state supercapacitors reported in the literature, and retains good charge and discharge performance under different bending conditions. The synthesis strategy reported here may be beneficial to the low-cost mass production of nanostructured electrode materials for energy storage applications.