The development of more efficient electrode materials is essential to obtain vanadium redox flow batteries (VRFBs) with enhanced energy densities and to make these electrochemical energy storage devices more competitive. A graphene-modified graphite felt synthesized from a raw graphite felt and a graphene oxide water suspension by means of electrophoretic deposition (EPD) is investigated as a suitable electrode material in the positive side of a VRFB cell by means of cyclic voltammetry, impedance spectroscopy and charge/discharge experiments. The remarkably enhanced performance of the resultant hybrid material, in terms of electrochemical activity and kinetic reversibility towards the VO2+/VO2+, and mainly the markedly high energy efficiency of the VRFB cell (c.a. 95.8% at 25 mA cm−2) can be ascribed to the exceptional morphological and chemical characteristics of this tailored material. The 3D-architecture consisting of fibers interconnected by graphene-like sheets positively contributes to the proper development of the vanadium redox reactions and so represents a significant advance in the design of effective electrode materials.The authors thank MINECO (projects MAT2013-48107-C3-1-R, INNPACTO IPT-2011-\ud 1690-920000 and NANO-EN-ESTO MAT2010-2015), Principado de Asturias (Fondo\ud Europeo de Desarrollo Regional: GRUPIN 14-118) and the European Regional Development\ud Funds (ERDF, FEDER Programa Competitivitat de Catalunya 2007-2013) for their financial\ud support.Peer reviewe