We report a facile fabrication of a high-performance supercapacitor (SC) using a flexible cellulose-based composite film of polyaniline (PANI), reduced graphene oxide (RGO), and silver nanowires (AgNWs). The flexibility, high capacitive behavior, cyclic stability, and enhanced rate capability of the entire device make it a good candidate for flexible and wearable SCs. Our results demonstrate that a capacitance as high as 73.4 F/g (1.6 F/cm2) at a discharge rate of 1.1 A/g is achieved. In addition, the SC shows a power density up to 468.8 W/kg and an energy density up to 5.1 Wh/kg. The flexibility of the composite film is owing to the binding effect of cellulose fibers as well as AgNWs. The superb electrochemical performance of the device is found to be mainly attributed to the synergistic effect between PANI/RGO/AgNWs ternary in a cushiony cellulose scaffold and porous structure of the composite.