Spectroscopic properties of Ag/Er co-doped thin plates of silicate glass were investigated with the aim of assessing the effective role of silver as a sensitizer for erbium. Additive heat treatments in air at different temperatures were performed on both a silver-exchanged and a silver-free plate in order to promote the formation of silver nanoparticles in the former and to refer to the later in the spectroscopic characterization. Absorption as well as photoluminescence and lifetime measurements in the region of the 4 I 13/2 ! 4 I 15/2 transition of the Er 3+ ion were performed; excitation wavelengths in the range from 360 to 750 nm were used. Enhancement of the Er 3+ luminescence at 1.53 lm was observed when the excitation wavelength was in the blue region. This spectral range typically coincides with the excitation energy of the surface plasmon resonance of nanometer-sized spherical silver particles.