Graphene and fullerene are remarkable nanostructures that have received tremendous attention in recent decades. Both graphene and fullerene are nanocarbon structures. Linking of graphene and fullerene may be through physical or chemical interactions. Various theoretical, simulation, modeling, and practical studies have been performed on graphene–fullerene bi-nanostructures. The most important application of graphene–fullerene and graphene oxide–fullerene hybrids is as reinforcement in polymer matrices. Consequently, this chapter highlights several essential aspects of graphene–fullerene and graphene oxide–fullerene hybrids with special emphasis on polymer/graphene–fullerene and polymer/graphene oxide–fullerene nanocomposites. The hybrids based on two nanocarbons (graphene–fullerene) may act as marvelous nanobifillers and lead to synergistic effects in physical property enhancement. Dramatic improvements in nanocomposite features are due to the molecular level interactions between the matrices and the hybrids. However, the major challenges involved in the processing of these nanocomposites are the dispersion/solubility of the nanobifiller hybrid and the interfacial adhesion between the matrix and nanobifiller hybrid. These challenges can be overcome by forming the physically or covalently linked functional hybrid networks accountable for the improved physical properties of the nanocomposites. Finally, the practical and future prospects of the polymer/graphene–fullerene and the polymer/graphene oxide–fullerene nanocomposites have been summarized hoping to facilitate the progress in this emerging area of nanocomposite technology.