We report a fully additive-based electrochemical approach to the site-selective deposition of silver on a polyimide substrate. Using a cathode coated with ion-doped precursor polyimide layers, patterns of metal masks used as anodes were successfully reproduced at the cathode precursor interface through electrochemical and ion-exchange reactions, which resulted in the generation of silver patterns on the polyimide films after subsequent annealing and removal from the substrate. Excellent interfacial adhesion was achieved through metal nanostructures consisting of interconnecting silver nanoparticles at the metal polymer interface, which are electrochemically grown "in" the precursor layer. This approach is a resist- and etch-free process and thus provides an effective methodology toward lower-cost and high-throughput microfabrication.