Low extracellular electron transfer performance is often a bottleneck in developing high‐performance bioelectrochemical systems. Herein, we show that the self‐assembly of graphene oxide and Shewanella oneidensis MR‐1 formed an electroactive, reduced‐graphene‐oxide‐hybridized, three‐dimensional macroporous biofilm, which enabled highly efficient bidirectional electron transfers between Shewanella and electrodes owing to high biomass incorporation and enhanced direct contact‐based extracellular electron transfer. This 3D electroactive biofilm delivered a 25‐fold increase in the outward current (oxidation current, electron flux from bacteria to electrodes) and 74‐fold increase in the inward current (reduction current, electron flux from electrodes to bacteria) over that of the naturally occurring biofilms. Shocking bacteria! The title biofilm was constructed by the one‐step in situ bioreduction and self‐assembly of graphene oxide (GO) with Shewanella oneidensis. The resulting 3D macroporous rGO/bacteria hybrid biofilm gave a 25‐fold increase in maximum oxidation current in microbial fuel cells, and a 74‐fold increase in reduction current in microbial electrosynthesis over that of the naturally occurring biofilms.