Ni_3−xCo_xS₄ (x = 1.5, 2, 2.25, 2.5) nanotube arrays were prepared on carbon cloth by a two-step hydrothermal route and their electrochemical performance was studied. The aspect ratios and electrochemical performance of the Ni–Co sulfide nanotube arrays can be well controlled by manipulating the Co/Ni molar ratio. With the cooperation of the appropriate morphology and compositions, the specific capacitance of Ni_0.75Co_2.25S₄ can reach as high as 1856 F g⁻¹ at 1 A g⁻¹. The rate capability is 88% at a high current density of 50 A g⁻¹. The superior electrochemistry performance demonstrates that Ni–Co sulfide nanotube arrays with an appropriate molar ratio of Co/Ni would be promising for high-performance supercapacitor materials.