Dispersions of Pd-NiO nanoparticles were electrochemically synthesized in a water-in-oil microemulsion, with fine control by appropriate adjustment of the concentration ratio of H(2)O to surfactant. The feasibility of using these Pd-NiO nanoparticles as a new activator for electroless Ni deposition (END) was examined. In this study, fast electroless deposition was achieved using Pd-NiO nanoparticles as a catalyst. A systematic study of the deposition kinetics and the mass activity by electrochemical quartz-crystal microgravimetry indicated that adding NiO to active colloids can shorten the induction time, and that reducing the particle diameter can accelerate END reactions because steady-state deposition is achieved more quickly. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3622844] All rights reserved.