This investigation focuses on the incorporation of sulfonated graphene oxide (sGO) to improve the performance of sulfonated poly(styrene-isobutylene-styrene) (SO3H SIBS) as a proton exchange membrane (PEM) for direct methanol fuel cell (DMFC) applications. The polymer nanocomposite membranes (PNMs) were evaluated as a function of the sulfonation level (37, 61, and 88 mole%) and GO/sGO level (1, 3, 5 and 10 wt.%). Functionalized GO was characterized using Fourier-Transform Infrared Spectroscopy (FT-IR) and Thermal Gravimetric Analysis (TGA). The PNMs were characterized to understand their morphology, proton transport and resulting nanostructures. The Ion Exchange Capacity (IEC), Water Absorption (WA), Water Content (WC), and Swelling Ratio (SR) of the PMNs were measured. The effect of temperature in the PNMs was addressed. Fenton’s test was utilized to evaluate the oxidative stability of the PNMs. In addition, the methanol permeability (PM) of the resulting membranes was also measured. Unique interactions arose between GO/sGO and the ionic groups in the polymer matrix influencing the transport mechanism of methanol and possibly protons. The intellectual merit of this investigation is the development of novel PEMs with unique ionic domains to enhance DMFC applications, while understanding how critical parameters (e.g., chemistry, water absorption and morphology) affect the proton transport mechanism within the membranes.