Reduced graphene oxide (RGO) was prepared by the reduction of graphene oxide (GO) with rhodanine. During the reduction, rhodanine was converted into polyrhodanine via oxidative polymerization initiated by GO, and the RGO was subsequently decorated with polyrhodanine. The reduction process and polymerization have been verified. Rhodanine reduced GO with high efficiency. Additionally, rhodanine is polymerized during the GO reduction process. The wrapping of polyrhodanine onto RGO is also verified. Using this novel modification process, the elastomer/graphene composites were prepared by the in situ interfacial modification of elastomer/GO compounds with rhodanine during the processing. Because of the unique reactivity of polyrhodanine during curing, strong interfaces were observed to form in the resulting elastomer/RGO composites. Furthermore, because of the substantially improved interfacial adhesion, combined with the improved dispersion state, the elastomer/RGO composites exhibited significantly improved mechanical properties compared with the elastomer/GO composites. Regarding the facile process and strikingly high modification efficiency, the present work offers new insight into designing high-performance elastomer/graphene composites by combining interfacial chemistry and curing chemistry.