Manganese dioxide–doped bismuth cobalt oxyhydroxide (MnO₂–BiCoOOH) nanostructures were successfully synthesized via a hydrothermal route. The obtained samples were characterized using XRD and FESEM analyses and subsequently employed for electrode fabrication in supercapacitor applications. The engineered morphology provides abundant electrochemically active sites, enabling rapid charge transfer and efficient charge-storage behavior. The fabricated electrode delivered a specific capacitance of 750 F g⁻¹ at 1 A g⁻¹ in 1 M KOH electrolyte, along with excellent cycling stability. These findings highlight that MnO₂ doping in BiCoOOH frameworks significantly enhances electrochemical performance, positioning them as promising candidates for advanced energy storage devices.