We report on localized surface plasmon resonance (LSPR) of silicon nanowires decorated with silver nanoparticles. Hydrogen peroxide in metal-assisted-etching method degenerates the surface of nanowires and creates oxygen-related defect sites. These defect sites enhance the infrared absorption at higher frequencies and emit visible light by band-to-band radiative recombination. Moreover, an almost 50-fold enhanced LSPR was obtained for 24 nm thick silver deposited 5 mu m long silicon nanowires. This enhancement was attributed to the change in the dielectric constant of effective medium created by defect states. LSPR wavelength could be tuned by changing the silver particle size and nanowire length. (C) 2013 AIP Publishing LLC.