Engineering plasmonic nanoparticles (NPs) into superstructures comprising two or more distinctive materials is highly desirable because these assemblies can unfold new properties that differ from those exhibited by their individual counterparts. In addition, metal NPs such as Au NPs and Ag NPs have played a major role in environmental remediation. In this study, we designed a heterogeneous NP assembly composed of an Au core and Ag satellite by utilizing a mussel-inspired polydopamine (PDA) strategy. This approach afforded substantial enhancement in the catalytic activity because of the synergistic effect between the Au core and Ag satellite. Specifically, the heat from the localized surface plasmon resonance excitation of the Au NPs can accelerate the reduction reaction of 4-nitrophenol, while the Ag NPs act as a catalyst for reducing the activation energy. Overall, we prepared a facile route to produce heterogeneous metal NP assemblies, which offers promise in scalable synthesis and application in heterogeneous catalysis.