Temperature–dependent Raman studies of disodium dimolybdate (Na2Mo2O7) crystal are reported. Lattice dynamical calculation was used to predict both wavenumbers and atomic displacements (eigenvectors) for the vibrational modes. These calculations were based on the classical rigid-ion model. The high-temperature Raman scattering study of the crystal showed that it remains in the orthorhombic structure in the 8–848 K range and undergoes a structural phase transition between 848 and 854 K. This phase transition is most likely connected with weak tiltings and/or rotations of both MoO4 (tetrahedra) and MoO6 (octahedra) units, which lead to a disorder in the oxygen sublattice. Copyright © 2010 John Wiley & Sons, Ltd.