<p>Silicon oxycarbide (SiOC) ceramic microspheres were synthesized via an ammonia-catalyzed sol–gel process and SiOC-derived carbon (SiOC-DC) materials were then obtained through a NaOH-assisted hydrothermal etching route. The NaOH-assisted hydrothermal etching removes most of the Si–C and Si–O bonds, enhances the degree of graphitization, and introduces oxygen-containing functional groups. Meanwhile, the Si–OH bond, the specific surface area, and micropore volume increase as the rising NaOH concentration. SiOC ceramics prepared at 1200&#xa0;°C (SiOC-1200) are more susceptible to NaOH etching, and the optimized SiOC-DC material etching from 1&#xa0;mol L⁻¹ NaOH solution achieves a high specific surface area of 573.35 m²&#xa0;g⁻¹ and a micropore volume of 0.16 cm³&#xa0;g⁻¹. It delivers a specific capacitance of 169.8 F g⁻¹ at 0.1 A g⁻¹ in a three-electrode system and retains 99.9% of its capacitance after 5000 cycles. In a symmetric supercapacitor, it attains 10.8 F g⁻¹ at 0.1 A g⁻¹ and maintains 99.44% capacity retention after 10,000 cycles at 0.5 A g⁻¹. The high specific surface area and micropore volume favor the improvement of supercapacitor performance.</p>