Stoichiometric In2S3 films were prepared by thermal evaporation technique onto clean glass substrates. According to X-ray investigations, the as-deposited films were in amorphous state. Both the ac conductivity and dielectric constants were measured in the frequency range 100 Hz−100 kHz at different temperatures. Different parameters such as the frequency exponent parameter s, the density of states near the Fermi level $N(E_{\rm F})$, the activation energy $(\Delta E)$ and the optical band gap Eg of In2S3 amorphous thin films were estimated. The hopping conduction was recognized as the conduction mechanism for the investigated films.