A novel solid-state method has been developed for synthesizing nickel oxide (NiO)/carbon nanotubes (CNTs) composite using an ionic liquid (IL, 1-butyl-3-methylimidazolium chloride) as the reaction medium. Ultraviolet-visible (UV-vis) absorbance spectroscopy, infrared spectroscopy (IR), and scanning electron microscopy (SEM) were employed to investigate the structure, morphology, and formation mechanism of the synthesized sample. The results demonstrated that the IL is effective for dispersing CNTs, which allows the tethering of nickel (II) ions onto the surfaces of the CNTs and facilitates the subsequent chemical deposition of NiO to obtain the NiO/CNTs composite. The electrochemical properties of the composite were determined using cyclic voltammetry and galvanostatic charge/discharge measurements in 6 M KOH. Because of its unique structure, the prepared NiO/CNTs electrode exhibited good capacitive behavior and cyclability. The high specific capacitance (521 F g(-1)) and good rate capability (91% capacity retention at 0.5 Ag-1) of the NiO/CNTs composite enable its use as a practical supercapacitor electrode material.