Silver and erbium co-doped sodium metaphosphate glasses were prepared by standard melt-quench technique. The samples underwent heat or 355 nm laser radiation exposure treatments in order to promote silver clustering. Absorption and photoluminescence spectra allowed distinguishing several active species related to silver, whose concentration in the samples depends on the treatment. A broad emission of silver related species has been detected in the visible region of the spectrum. The excitation spectra of the band and of the 1.5 μm luminescence of Er demonstrated energy transfer from Ag aggregates to Er. Differently from silicate glasses, in phosphates the silver to erbium energy transfer is very weak.