The transition-metal (oxy)hydroxides have been considered as one of the promising electrocatalysts for oxygen evolution reaction (OER). Therefore, it is necessary to have in-depth study on the origin behind their favorable inherent OER activity and further improve their catalytic performance. Herein, nickel–cobalt-vanadium trimetallic (oxy)hydroxide nanosheets decorated with silver nanoparticles (Ag NPs) (Ag@NiVCo) are fabricated for OER by a simple spontaneous redox reaction. The Ag@NiVCo can deliver an overpotential of only 255 mV at 10 mA cm and a small Tafel slope of 38.3 mV dec in alkaline solution. We accredit the outstanding catalytic performance to the following aspects: (1) the active (oxy)hydroxide layer on the surface of Ag@NiVCo generated through the surface reconstruction, (2) the optimal local coordination induced by the interaction between Ag NPs and trimetallic system, (3) the extensively exposed active sites, and (4) the significantly improved charge-transfer ability due to the incorporation of Ag NPs. Our findings may provide deep understanding on the mechanism of OER and offers a novel strategy to design electrocatalysts with superior OER activity.