Previous ultrasonic measurements have shown a softening of one of the acoustic‐phonon branches in thallium phosphorus selenide (Tl3PSe4) when subject to hydrostatic pressure. These measurements also show a 60% softening between room temperature and 90 K. In order to further characterize this material and to investigate the possibility of a phase transition at temperatures less than 90 K, we have used inelastic neutron scattering to measure the phonon dispersion along symmetry directions. The measurements agree well with the ultrasonic measurements previously reported for all branches except the soft ab shear described by the strain componente6. The ab shear is found to be 60% stiffer than the ultrasonic value with very little temperature dependence.