Conductive carbon-polymer composite electrodes for the vanadium redox flow battery were developed and their properties investigated. Conductive polymer composite materials were fabricated by mixing PVC, nylon 6, nylon 11, LDPE, and HDPE with conductive fillers. To overcome the deterioration in the mechanical properties of carbon-polymer composites with high carbon loading, a range of chemically resistant rubbers was blended into the composites. Electrical, mechanical, permeation, and electrochemical studies show that the HDPE composite is the best electrode matrix material for the vanadium redox battery. The performance of a vanadium redox flow cell employing the best composite electrode was also evaluated and voltage efficiencies as high as 88% were obtained with electrodes employing graphite felt active layers banded to the carbon-polymer composite substrates.