A recent investigation of the (BaF2–MgF2) phase diagram produced several new compounds which are suitable hosts for Rare Earth impurities. We present results on single crystals of Ba2Mg3F10 doped with Eu2+. The local structure and optical properties of this system were investigated by luminescence emission and by EPR. We observed two different Eu2+ sites. Both show Cs point symmetry and an important ground state splitting. Correlating our EPR and optical results with the new Ba2Mg3F10 structure data allowed the assignment of each of them to a specific barium lattice site. The luminescence emission of both the 4f7–4f65d and the 4f7–4f7 transitions is observed. The relative importance of the two emissions is strongly temperature dependent. The emission intensities of the intra f-shell 6P7/2→8S7/2 transitions increase strongly on going from 295 K to 77 K. Thus, the lowest levels of the 4f65d configuration are approximately degenerate with the 6P7/2 manifold.