NaMnMoO3F3 center dot H2O was precipitated at low temperature from aqueous dissolutions of Na2MoO4 center dot 2H(2)O in aqueous HF (or NaHF2) using either Mn(CH3COO)(2)center dot 4H(2)O or MnF2 as manganese precursors. Chemical analysis, IR spectra, and effective paramagnetic moment are in agreement with the proposed formula Electron microscopy studies indicate that the sample is constituted of very thin Plate-like microcrystals. The average crystal structure (a = 3.5947(1), b = 21.246(1), and c = 7.3893(2) angstrom and Cmcm (No. 63) SG) has been elucidated through powder diffraction methods (synchrotron and neutron). Tiny superstructure peaks are observed that can be indexed with the space group Pbca and cell parameters a = 7.1894(2), b = 21.246(1), and c = 7.3893(2) angstrom. Electron diffraction confirms the doubling of a parameter. Ordering of O and F is proposed in agreement with Pauling's, rule and bond strength sums for each anionic position. The structure that is formed has a layered stacking arrangement along the b-axis. of the MnO4F2 octahedra layers that share corners along a- and c-directions: The large interlayer space contains MoO4F2 octahedra (connected to the layer) together with sodium ions and water molecules, tentatively forming hydrogen bonding with fluorine anions. The origin of the superstructure could not be fully elucidated, but it is presumably related to slight distortions within the MnO4F2 octahedra.