A synergistically integrated graphene-based ternary composite (rG-Cu) consisting of uniform natural polydopamine (Pdop)-functionalized graphene sheets (Dop-rG) and well-dispersed Cu nanoparticles (NPs) has been developed. By a one-step reduction and modification of graphene oxide with dopamine, water-dispersible Dop-rG was first prepared. Cu NPs were then incorporated homogeneously onto Dop-rG by a simple solution route leading to activated rG-Cu, which showed an ultrahigh catalytic activity and good reusability for catalytic reductions of different types of dyes, including methylene blue and azo-based acid and reactive dyes. It took only 30 s for complete reduction of methylene blue. In addition to the main action of the catalytically active component of the well-dispersed Cu NPs, the uniform adhesive Pdop layer and graphene base with large surface area and superior electron-transfer capacity are also believed to assist synergistically the catalytic reduction. The work has opened up a new avenue for synthesis of a graphene-based ternary composite with extraordinary catalytic activity for practical applications in addressing environmental protection issues.