Enhanced Eu3+ luminescence by three Ag species in transparent Ag–Eu3+ co-doped oxyfluoride glasses was investigated systematically. Under 464 nm excitation, enhancement of Eu3+ luminescence (four times) is attributed to local-field surface plasmon resonance (SPR) effect of Ag nanoparticles (NPs). Under 350 nm excitation, significant enhancement of Eu3+ emission (540 times) is assigned to energy transfer (ET) from very small molecule-like, nonplasmonic Ag particles (ML-Ag) to Eu3+. Under 270 nm excitation, big enhancement of Eu3+ luminescence (75 times) is ascribed to ET from isolated Ag+ to Eu3+. Our research may extend the understanding of interactions between Ag species and Eu3+.