The title compound is an AB-type salt with a completely ordered anion sublattice. Because of the strong trans influence of the Br ligands, both Os-Br bonds, of 2.466 (1) and 2.468 (1) Angstrom, are shortened compared with those reported for K-2[OsBr6] (2.51 Angstrom). However, only one of the two F Ligands coordinated trans to a Br ligand exhibits a longer Os-F distance [1.968(4) Angstrom] than those along the symmetrically coordinated F-Os-F axis [1.930(4) and 1.929(4) Angstrom].