Small, uniform Ag nanoparticles (NPs) in ionic liquids (ILs) are synthesized via simple sputtering route. The NPs embedded in polymer film are coated on top of InGaN/GaN active multiple quantum‐well light‐emitting structures and their optical characteristics are compared. The InGaN structures coated with Ag NPs show a significant increase in photoluminescence efficiency, mainly caused by localized surface plasmon (LSPs) coupling. Time‐resolved (TR) photoluminescence analysis demonstrates that the coupling efficiency is 47.2%. The increased luminescence is caused by good energy matching between the surface plasmon and the light emitter. The authors believe that present work takes a first step to utilize the advantages of metal NPs synthesized in ILs and has a great potential for use in various optoelectronic devices.