Ti₃C₂T_x and Ti₃C₂T_x-NiO composites with three-dimensional (3D) porous networks were successfully fabricated via vacuum freeze-drying. The microstructure, absorption, and electrochemical properties of the developed composites were investigated. Nickel oxide (NiO) nanoparticles could be evenly distributed on the three-dimensional network of three-dimensional Ti₃C₂T_x using solution processing. When employed as electrochemical capacitor electrodes in 1 M environmentally friendly sodium sulfate, Na₂SO₄, solution, the three-dimensional porous Ti₃C₂T_x-NiO composite electrodes exhibited considerable volume specific capacitance as compared to three-dimensional porous Ti₃C₂T_x. The three-dimensional porous Ti₃C₂T_x-NiO composite delivered a remarkable cycling performance with a capacitance retention of up to 114% over 2500 cycles. The growth trend of the capacitance with NiO content shows that nickel oxide plays a crucial role in the composite electrodes. These results present a roadmap for the development of convenient and economical supercapacitors in consideration with the possibilities of morphological control and the extensibility of the process.