The adhesion of conductive patterns printed on polymer substrates is an indispensible issue for the commercialization of printable and flexible electronic devices. Plasma treatment has been widely used to improve the interfacial adhesion between a metal and a flexible polymer substrate. This study aims to investigate the influence of a polymerized acrylic acid layer coated by atmospheric-pressure plasma (APP) on the adhesion of a screen-printed silver (Ag)/polyimide (PI) system. The acidic oxygen-containing functional groups were incorporated onto a PI film by plasma polymerization of acrylic acid and, on it, the conductive tracks were constructed with a Ag nanopaste via screen printing. The Ag tracks were sintered at various temperatures ranging from 150 to 300 degrees C for 30 min in air. The adhesion was evaluated by a roll-type 90% peel test. The peel strength of the screen-printed Ag/PI system with the acrylic acid film approximately quadrupled. To understand this adhesion enhancement, field emission scanning microscopy (FE-SEM), atomic force microscopy (AFM), contact angle analyzer, and X-ray photoelectron spectroscopy (XPS) were utilized. It was confirmed from these analyses that a hydrophilic film was formed due to the plasma polymerization process, and the carbon-oxygen (C-0) and carbonyl (C=0) bonds increased at the interfacial surface. Under the optimized conditions, a maximum adhesion of 245.5N/m was obtained, and the stronger adhesion with the acrylic acid coating influenced the improvement in the flexibility of the film.