The direct reaction of hydrogen on a mixture of Na + Mg or NaF + Mg allowed for synthesis of NaMgH3 and NaMgH2F, respectively. Both phases were indexed with an orthorhombic unit cell with dimensions a = 546.34, b = 770.30, c = 541.08 pm for NaMgH3 and a = 547.59, b = 769.68, c = 540.31 pm for NaMgH2F. The crystal structures were refined by X-ray Rietveld refinement. They derive from the perovskite structure type by a Pmm --> Pnma distortion. In the hydridofluoride, H- and F- anions are equally distributed in the two anionic sites in a disordered way.