Glasses activated with Eu 3+ ions are attractive as luminescent materials for various photonic applications. Co-doping with copper has been proposed for enhancing material optical properties, but the quenching effect of Cu 2+ impurities on Eu 3+ emission in glass remains largely unexplored. In this work, Eu 2 O 3 /CuO-containing barium–phosphate glasses have been prepared by the melt-quench method, and the Eu 3+ photoluminescence (PL) quenching resulting from Eu 3+ →Cu 2+ energy transfer was evaluated. Optical absorption spectroscopy showed that with the increase in CuO concentration the Cu 2+ absorption band resonant with Eu 3+ emission (e.g. 5 D 0 → 7 F 2 transition around 615nm) developed steadily. As a result, Eu 3+ PL was progressively quenched. Evaluation of the quenching constants as a function of temperature in the 298–673K range showed differences basically within experimental error, consistent with a resonant transfer and lack of phonon-assisted processes. Moreover, analysis of the Eu 3+ emission decay dynamics revealed a strong correlation between the decay rates and Cu 2+ impurity levels. Results imply that for practical applications the levels of Cu 2+ in Eu 3+ /Cu + -activated glasses should be reduced if not removed as these will significantly limit device efficiency.