Polypyrrole (PPy)@cellulose fiber-based composites have been widely investigated as electrode materials for use in flexible supercapacitors. However, they cannot readily provide high specific capacitance and cyclic stability owing to their inherent drawbacks, such as high resistance, Weber impedance, and volume expansion or collapse during charging/discharging. In this study, iron oxyhydroxide (FeOOH) is incorporated in the abovementioned composite to decrease the equivalent series resistance, charge transfer resistance, and Weber impedance, thereby enhancing electron transfer and ion diffusion, which results in superior electrochemical performance. The PPy-wrapped FeOOH@cellulose fiber-based composite electrode with the molar ratio of FeSO₄ to NaBH₄ of 1∶1 exhibits a high specific capacitance of 513.8 F/g at a current density of 0.2 A/g, as well as an excellent capacitance retention of 89.4% after 1000 cycles.