Development of a proton exchange membrane (PEM) with insignificant methanol permeability at highly concentrated methanol supply is considered a major advancement in the direct methanol fuel cell (DMFC) technology. Here, we investigate the potential of graphene-based membranes for achieving this objective. A membrane is prepared through the lamination of graphene-oxide (GO) nanoplatelets and its transport characteristics are studied. The studies suggest that the membrane methanol permeation rate decreases linearly as the nanoplatelets size is increased, while proton conductivity changes rather insignificantly. The observed transport characteristics are attributed to either different adopted conduction pathways or surface mobility of protons and methanol molecules. The findings imply that the GO nanoplatelets contain atomic formations that are more selective to protons than to methanol molecules. Direct methanol fuel cell measurements of the membrane at high fuel concentrations showed almost no drop in the open circuit potential (OCP) and significant improvements in power density compared to that of a Nafion membrane. Published by Elsevier B.V.