In this study, plasmonic freestanding InGaN/GaN multi-quantum well (MQW) microdisks were fabricated on Si (111) pedestals using wet chemical undercut etching, followed by decorating of Ag nanoparticles on microdisks to improve whispering gallery mode (WGM) resonance emission. The enhancement resulted from the plasmonic coupling effect between excitons in MQWs and localized surface plasmons of Ag. The radial resonance of WGMs from optically pumped microdisk cavities were observed in the photoluminescence spectra at a threshold optical pumping power density of 4.7 kW/cm with a WGM mode spacing of Δλ = 1.3 nm.