Polymer-semiconductor composites are prepared from a homogeneous mixture of powders of high-density polyethylene (HDPE) and the TlInS2 semiconductor. The electric conductivity (σac) and dielectric properties (ɛ′ and ɛ″) of the composites as a function of the volume fraction of the TlInS2 ferroelectric (0–60%), temperature (20–150°C), and frequency (102–106 Hz) of the measured electric field are studied. The semilogarithmic plot of the temperature dependence of conductivity, i.e., the lnσac-temperature curve, comprises three regions; one of them corresponds to the low temperature portion of the curve where σac weakly depends on temperature, while in the other two regions σac exhibits a strong temperature dependence. The plot of the frequency dependence of σac for the HDPE-TlInS2 composites shows that σac increases exponentially and nonlinearly at low and high frequencies, respectively. The observed decrease in ɛ′ with increasing frequency is representative of a dielectric relaxation process. The occurrence of this relaxation process is also confirmed by the fact that the ɛ"(f) plot exhibits a maximum at 10 kHz. It is assumed that the relaxation processes in the HDPE-TlInS2 composite structures are attributed to interfacial polarization and the local mobility of the polar components and short segments of the polymer backbone.