Abstract The dielectric properties of TlSbSe 2 have been studied at microwaves in a wide temperature region. It is shown that the crystal possesses a high and anisotropic dielectric permittivity caused by phonons contribution. The temperature dependence of the dielectric permittivity in the polar direction according to the Curie-Weiss law with the negative Curie temperature shows that TlSbSe 2 is a virtual ferroelectric. Between 4.2 and 700 K the crystal has a sequence of structural phase transitions, including the phase transition to a supposed incommensurate and superionic phase. The phase transition cause anomalies of the permittivity and electric conductivity of the crystal.