Two isostructural tellurium-rich tellurites, Na2WTe4O12 (1) and Na2MoTe4O12 (2), have been synthesized and structurally characterized by single-crystal X-ray diffraction studies. Three types of polyhedra, namely, MO6 octahedra, TeO3 pyramids, and TeO5 square-pyramids, constitute the three-dimensional (MTe4O12)(2-) (M = W, Mo) anionic framework, which contains different types of intersecting tunnels, one of them being novel spiral pseudohexagonal tunnels occupied by sodium ions. Both compounds have the monoclinic space group C2/c, with Z = 4. The lattice parameters are as follows: for 1, a = 17.348(3) Angstrom, b = 5.7755(10) Angstrom, b = 11.269(3) Angstrom, beta = 104.33(2)degrees; for 2, a = 17.341(4) Angstrom, b = 5.8262(11) Angstrom, c = 11.268(2) Angstrom, beta = 104.58(2)degrees. Syntheses and structure, powder X-ray diffraction, and infrared spectroscopic studies of these compounds are described.