An optical investigation of the properties of europium (II) ions introduced in Ba₂Mg₃F₁₀ single crystals is presented. The spectra and time-dependence of both the inter-configurational (f–d) and the intra-configurational (f–f) transitions are described. The emission spectrum consists of two emitting Eu²⁺ centres, each showing one broad f–d band and one ⁶P_7/2 quartet. The thermal equilibrium between the f–f and f–d emitting states is investigated and found to take place on a microsecond timescale for one of the two Eu²⁺ centres. The spectroscopic results combined with numerical modelling of the influence of the host crystal on the ⁶P_7/2 energy scheme allow the assignment of each f–f and f–d emission to its corresponding Eu²⁺ centre.