The conductivity of tetramethylammonium fluoride tetrahydrate (TMAF4) has been studied by impedance spectroscopy in the temperature range 213-322 K. The response of the cell Au TMAF4 Au is typical for a polycrystalline electrolyte between solid blocking electrodes and it is temperature dependent. A conductivity drop of about two orders of magnitude is observed at temperatures around the melting point of TMAF4. Linear Arrhenius-type conductivity dependence is observed for the temperature ranges corresponding to the high and low temperature phases of solid TMAF4. The corresponding activation energies of conductivity are equal to 1.93 eV and 0.48 eV. The conductivity of TMAF4 is substantially lower than that of tetramethylammonium hydroxide pentahydrate (TMAOH5). However, TMAF4 can also be used in electrochemical studies. The reasons for the difference in conductivity between TMAF4 and TMAOH5 are discussed in terms of their crystallographic structures.