Polycrystalline pyridinium periodate has been studied over a wide range of temperature by differential thermal analysis, proton nuclear magnetic resonance (NMR) spectra and relaxation and complex dielectric permittivity measurements. Two solid-solid phase transitions at 210 and 323 K have been revealed and the pyridinium cation reorientation in all three phases characterized. The polar properties of the intermediate phase have been demonstrated. The upper phase transition temperature appears to be the Curie point of a new ferroelectric compound.