Electrochemical surface charge-induced variation of physical properties in interface-dominated bulk materials is a rapidly emerging field in material science. The recently developed three-dimensional bulk nanographene (3D-BNG) macro-assemblies with ultra-high surface area and chemical inertness offer new opportunities in this area. Here, the electronic transport in centimeter-sized 3D-BNG monoliths can be dynamically controlled via electrochemically induced surface charge density. Specifically, a fully reversible variation in macroscopic conductance up to several hundred percent is observed with 1 V applied gate potential. The observed conductivity change can be explained in the light of the electrochemically-induced accumulation or depletion of charge carriers in combination with a large variation in the carrier mobility; the latter, being highly affected by the defect density modulations resulting from the interfacial charge injection, sharply decreases with an increase in defect concentrations. The phenomenon presented in this study is believed to open the door to novel applications of bulk graphene materials such as, for example, low voltage and high power tunable resistors.