The title compound, lithium/sodium iron(III) bis-[ortho-molyb-date(VI)], was obtained by a solid-state reaction. The main structure units are an FeO6 octa-hedron, a distorted MoO6 octa-hedron and an MoO4 tetra-hedron sharing corners. The crystal structure is composed of infinite double MoFeO11 chains along the b-axis direction linked by corner-sharing to MoO4 tetra-hedra so as to form Fe2Mo3O19 ribbons. The cohesion between ribbons via mixed Mo-O-Fe bridges leads to layers arranged parallel to the bc plane. Adjacent layers are linked by corners shared between MoO4 tetra-hedra of one layer and FeO6 octa-hedra of the other layer. The Na(+) and Li(+) ions partially occupy the same general position, with a site-occupancy ratio of 0.631 (9):0.369 (1). A comparison is made with AFe(MoO4)2 (A = Li, Na, K and Cs) structures.