The infrared (700–100 cm −1) vibrational spectra of single crystals and powders of the transition metal thiophosphates, MPS 3 (M = Mn, Fe and Ni) have been studied as a function of temperature. The spectra of the three compounds show strong similarities both in the position and intensity of the various bands. The only metal dependent feature is a band at ∼260 cm −1. A detailed analysis of the selection rules for the MPS 3 lattice has been carried out using the correlation method. From the expected orientational dependence it was possible to assign the various spectral features to the normal modes of the MPS 3 lattice. It was found that the spectra in the 700200 cm −1 limit could be consistently interpreted within an ionic model, M 2 2+ (P 2S 6) 4−.The normal modes being separable into the internal modes of the “ethane like” P 2S 6 group, which occur in the 700–300 cm −1 spectral region, those to the vibrations of the MS 6 polyhedra (∼260 cm −1) and to coupled modes occurring below 200 cm −1. The model successfully accounts for the gross similarity in the vibrational spectra of MnPS 3, FePS 3 and NiPS 3.