Flexible sheets consisting of acrylonitrile-butadiene rubber (NBR) and vapor-grown carbon fiber (VGCF) are newly prepared varying the composition (VGCF 20–30 wt.%) for use as a current collector of supercapacitor electrodes. The as-prepared VGCF/NBR is then electrodeposited by aniline using a potentiodynamic cyclic voltammetry to yield a polyaniline (PANI)/VGCF/NBR composite electrode. It is confirmed that the electrical conductivity of VGCF/NBR current collector can be enhanced as the content of VGCF increases. Cyclic voltammetry result for the PANI/VGCF/NBR composites shows that the sample with 30 wt.% VGCF achieves a maximum specific capacitance (271.8 F g−1) at 5 mV s−1 and also reaches a superior specific capacitance at high scan rates. Such supercapacitor performance is possibly originated from the synergistic effect consisting of higher polarity of nitrile groups in NBR, conducting pathway of VGCF, and electroactive property of PANI.