Bacterial cellulose (BC) has attracted much attention due to its low-cost, high specific surface area and ample porosity. In this work, polypyrrole (PPy) and cobalt sulfide (CoS) have been deposited on BC membranes to prepare the nanofibrous composite electrodes of PPy/CoS/BC with excellent flexibility for supercapacitor application. The introduction of CoS remarkably improves the pseudocapacitance and electrochemical stability of PPy/BC-based electrodes. The specific capacitance of the PPy/CoS/BC-based supercapacitors can reach to about 614Fg−1 at a current density of 0.8mAcm−2 (0.70Ag−1) with maintaining 62.4% of the original value after 300 cycles; while the PPy/BC-based device could retain only 21.7% after 300 cycles. The PPy/CoS/BC-based devices can exhibit an energy density of about 54.5Whkg−1 at a power density of 663Wkg−1. This work provides a promising approach to fabricate cost-effective and flexible membranes which can be used as high-performance supercapacitor electrodes.