Abstract [C6H18N3]BiCl6 crystallizes at room temperature in the monoclinic space group P21/n. The crystal is built up of separated BiCl63− octahedral anions and 1-(2ammonium-ethyl) piperazindiium cations. Differential scanning calorimetry (DSC) disclosed structural phase transitions of the order–disorder type at 343 and 393K. Dielectric investigations revealed a step-wise change of the electric permittivity at Ttr1 and Ttr2, characteristic of crystals in the high-temperature phase. Temperature-dependant Raman spectra for polycrystalline samples were taken between 298 and 493K to clarify the cation dynamics contribution to the mechanism of the phase transition. The modes are assigned to the deformation vibrations of the anionic group and NH+, NH2+ and NH3+ groups in the 1-(2ammonium-ethyl) piperazindiium cations. The 1-(2ammonium-ethyl) piperazindiium cations appeared to be the most sensitive to the phase transition.