High-quality amorphous NiO/C/carbon nanotubes (CNTs) composite with an irregular porous structure have been successfully synthesised by a one-step combustion process at 350°C for 2 h with a heating rate of 3°C/min in air. To fully understand the potential of NiO/C/CNTs, the phase composition, morphology and electrochemical properties of materials were investigated. Benefiting from the in situ formed carbon, the addition of the CNTs and the advantages of the porous structure, the materials have shown superior electrochemical properties for supercapacitors. The specific capacitance of the composite reaches up to 1618 F/g at a current density of 1 A/g. Furthermore, the NiO/C/CNTs||activate carbon asymmetric supercapacitor device demonstrates both a high energy density (25.9 Wh kg⁻¹) and power density (5570 W kg⁻¹), and delivers a better cycling stability (about 94%) after 7000 cycles, which is a potential material for further development of fabricating a supercapacitor electrode.