Butyl rubber, IIR nanocomposites based on modified graphene sheets, were fabricated by solution processing followed by compression molding. MG was prepared from natural graphite, NG through graphite oxide route. X-ray diffraction showed that the exfoliated MG was homogeneously dispersed in the IIR matrix with doping levels of 1-10 wt% as evidenced by the lack of the characteristic graphite reflection in the composites. In contrast, the graphite retained its stacking order and showed the sharp characteristic peak in the NG-IIR composites. Scanning electron microscope images of the fracture surfaces of the IIR matrix showed that MG nanofillers exhibited better compatibility than NG did. The mechanical properties of the MG-IIR nanocomposites were significantly improved due to the efficient distribution of the large surface area MG sheet. The tensile modulus of nanocomposite with doping level of MG 10 wt% was 16 times that of the pure IIR. POLYM. ENG. SCI., 51:2254-2260, 2011. (C) 2011 Society of Plastics Engineers