The frequency and temperature dependences of the permittivity and conductivity of FeGaInS4 single crystals in an ac current have been investigated. The permittivities of single crystals and activation energies of permittivity and conductivity are determined. It is established that the conduction of these crystals in the temperature range under study has an activation nature. A frequency dependence of the activation energy is observed, which is related to the decrease in the relaxation time of blocking layers with an increase in frequency.