Graphene oxide (GO)/carboxylated acrylonitrile butadiene rubber (xNBR) vulcanizates were prepared in this study by mixing exfoliated GO aqueous dispersion with xNBR latex. The GO monolayers were exfoliated from natural flake graphite by Hummers' method. This study shows that GO could be dispersed homogeneously in xNBR matrix up to 1.2 vol.%. Adding GO nanosheets has a great effect on the mechanical, thermal stability, thermal conductivity, and thermal diffusivity of GO/xNBR vulcanizates. With the incorporation of GO nanosheets, the thermal stability, thermal conductivity, and thermal diffusivity of GO/xNBR vulcanizates increased significantly. The mechanical property of GO/xNBR vulcanizates reached its peak with 1.2 vol.% of GO content. The addition of 1.2 vol.% of GO nanosheets largely enhanced the tensile strength and modulus at 100 % elongation of xNBR by more than 370 and 230 %, respectively. The thermal conductivity and diffusivity of the GO/xNBR vulcanizates with 1.6 vol.% of GO had 1.4- and 1.2-fold improvements, respectively, compared to that of unfilled xNBR vulcanizate.