Nanocomposite membranes are prepared by the dispersion of aspartic acid functionalized graphene oxide (ASPGO) in sulfonated poly(ether ether ketone) (SPEEK) for electrolytes in direct methanol fuel cells. Graphene oxide (GO) is prepared by modified Hummer's method and is further functionalized with aspartic acid. GO functionalization is confirmed from FT-IR, elemental analysis, XPS and TGA. Its morphology is confirmed by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). ASPGO is then incorporated in SPEEK matrix using solvent cast method to form composite membranes. The composite membranes are characterized in terms of their physico-chemical properties namely tensile strength, proton conductivity and methanol permeability. Addition of ASPGO improves the membrane dynamics by forming interfacial interactions with the host matrix in turn enhancing the proton transport and mitigating the methanol permeability through the membrane. These membranes are subjected as electrolytes in DMFC polarization studies and the results are compared with state of art Nafion-117 membrane.