Barium in BaMgF[4] and in Ba[6]Mg[7]F[26] can be partially replaced by Sr or Eu. The single crystal structural analysis of the title compounds (a = 409.06 pm, b = 1452.7 pm, c = 579.02 pm, space group Cmc2[1] for Ba[0.78(3)]Eu[0.22(3)]MgF[4] [Z = 2, R[w] = 0.023 for 998 reflections] and a = 583.47 pm, b = 1209.09 pm and c = 1506.56 pm, space group Immm for Ba[5.20(6)]Eu[0.80(6)]Mg[7]F[26]) MgF[4] [Z = 2, R[w] = 0.019 for 2694 reflections] confirms the substitution of barium by europium. A split refinement of the substituted barium site in both crystals reveals a trend of europium to get closer to the nearest fluoride neighbors by simultaneously reducing the coordination sphere.