The title mixed-alkali-metal molybdenium oxide, hexa-kis-(lithium/sodium) undeca-molybdate, was synthesized by solid-state reaction at 793 K. Its [Mo11O36](6-) framework is built up from MoO6 octa-hedra and MoO5 pyramids linked together by edges and vertices. The framework delimits two types of inter-secting tunnels running along [100] and [001], where the sodium and lithium ions are located. Two of the sodium ions and the lithium ion have fractional site occupancies. One of the Mo atoms has site symmetry 2, one sodium ion has site symmetry 2 and one has site symmetry -1, and the Li(+) ion has site symmetry 2. Structural relationships between the title compound and the anatase and Na6Mo11O36 structures are discussed.