Herein, we report on direct fabrication of silver circuit patterns on polyimide resin, the method of which relies on potassium hydroxide-induced chemical modification of the polyimide surface to introduce carboxylic acid groups and incorporation of silver ions through subsequent ion exchange followed by UV-irradiation-induced photochemical reaction. In this new, fully additive based strategy, silver thin films consisting of silver nanoparticles are successfully formed on the selected surface sites simply using a photomask. The thickness of modified layers and amount of incorporated silver ions can be systematically controlled through initial potassium hydroxide treatment, thus providing a better method for controlling the degree of metallization. Diffusion of silver ions in the modified polyimide layer during the reduction process is suggested to be responsible for the film formation and the resulting interfacial structures between silver thin films and underlying polyimide layers.