A novel electrochemical method for size-controlled synthesis of spherical silver nanoparticles in aqueous phase was developed for the first time. In this method the poly(N-vinylpyrrolidone) (PVP) was used as the stabilizer for the silver clusters. PVP was found to greatly promote silver particle formation rate and significantly reduce silver deposition rate, thereby making monodispersed silver nanoparticles to be synthesized very convenient by means of electroreduction of the bulk silver ions. It is possible to control the particle size by adjusting electrolysis parameters and to improve homogeneity of silver particles by changing the composition of electrolytic solutions. The results also showed the fact that the rate of transfer of PVP-stabilized silver clusters from the cathodic vicinity to the bulk solution played an important role in preparation of the monodispersed nanoparticles. In addition, the silver nanoparticles synthesized electrochemically may be directly employed to prepare the silver-doping tin electrodeposited coating.