The title compound, (C7H10N)2(H3O)2[Fe(CN)6] or (Etpy)2(H3O)2[Fe(CN)6] (Etpy+ is 1-ethylpyridinium), crystallizes in the space group Pnnm. The FeII atom of the [Fe(CN)6]4- anion lies on a site with site symmetry..2/m, and has an octahedral coordination sphere defined by six cyanido ligands. Both the Etpy+ and the oxonium cations are located on a mirror plane. In the crystal, electron-donor anions of [Fe(CN)6]4- and electron-acceptor cations of Etpy+ are each stacked parallel to the b axis, resulting in a columnar structure with segregated moieties. The crystal packing is stabilized by a three-dimensional O - H⋯N hydrogen-bonding network between the oxonium ions and the cyanide ligands of [Fe(CN)6]4-.