Sulfonated poly (vinylidenefluoride-co-hexafluoropropylene) (SPVdF-co-HFP) based polymer nano-composite proton exchange membranes (PEMs) were successfully fabricated in the presence of sulfonated graphene oxide (SGO) as nano-filler for direct methanol fuel cell (DMFC) applications. Sulfonation of GO was carried out using sulfanilic acid and the incorporation of -SO3H groups were confirmed by FTIR, HR-TEM and Raman spectroscopy. The physicochemical properties of the fabricated membranes such as ion exchange capacity (IEC), water uptake (WU), swelling ratio (SR), oxidative, thermal and mechanical stability, proton conductivity, methanol permeability and membrane selectivity were determined. Among the various nanocomposite PEMs were prepared, SPVdF-co-HFP/SGO-7 exhibited good tensile strength (29.7 MPa), improved Young's modulus (432.5 MPa), high proton conductivity (5.52 x 10(-3) S/cm, at 30 degrees C), superior selectivity (2.99 x 10(4) Scm(-3)s) and reduced methanol cross-over (1.846 x 10(-7)cm(2)s(-1)) and this nanocomposite membrane can possibly be a superior and alternate candidate to Nafion membrane in DMFCs. (C) 2018 Elsevier Ltd. All rights reserved.