Vertically aligned nickel–cobalt oxide (NCO) nanosheets with porous structure were successfully synthesized on FTO substrates by a simple electrochemical method without any templates. Cyclic voltammetry (CV) and galvanostatic charge/discharge measurements show that the porous NCO nanosheets have an ideal capacitive performance and long-term stability. With an optimum amount of Ni, the specific capacitance for the NCOs could reach as high as 453 F g−1 at a scan rate of 5 mV s−1 and 506 F g−1 at a current density of 1 A g−1, showing an improvement of around 50% compared with cobalt oxide. Furthermore, a symmetric supercapacitor based on two NCO electrodes exhibits a maximum specific capacitance of 89.2 F g−1 at 0.17 A g−1.