In this study, we investigated the addition of a tungsten catalyst into the electrolyte of a vanadium redox flow battery (VRBs) and measured the cell performance with respect to the concentration of the W6+ precursor. The VRBs showed a clear improvement in electrochemical performance because of the deposition of tungsten on the electrode. The presence of tungsten allowed the ionization of tungsten in the electrolyte during battery cycling. The optimized concentration of the tungsten additive was examined using electrochemical methods, which showed that the efficiency of the VRBs improved by 2–3% after the addition of 3mM tungsten to the electrolyte. In particular, the performance of VRB cells in an anolyte containing a W6+ catalyst was significantly enhanced at high current rates.