NiO-doped bismuth cobalt oxyhydroxide (NiO–BiCoOOH) nanostructures were successfully synthesized via a hydrothermal route. The obtained samples were characterized using XRD and FT-IR analyses and subsequently employed for electrode fabrication in supercapacitor applications. The engineered morphology provides abundant electrochemically active sites, thereby facilitating rapid charge transfer and enhanced charge-storage behavior. The fabricated electrode delivered a high specific capacitance of 700 F g⁻¹ at 1 A g⁻¹ in 1 M KOH electrolyte, along with excellent cycling stability. These results highlight the potential of NiO doping in BiCoOOH frameworks to improve electrochemical performance, making them promising candidates for next-generation energy storage devices.