Electrical conductivity, I-V characteristics and optical properties are investigated for InSbSe3 amorphous thin films of different thicknesses prepared by thermal evaporation at room temperature. The composition of both the synthesized material and thin films were checked by energy dispersive X-ray spectroscopy (EDX). X-ray analysis indicated that all samples under investigation have amorphous structure. The dc electrical conductivity was measured in the temperature range (303-393 K) and thickness range (149-691 nm). The activation energy Delta E (sigma) was found to be independent of film thickness in the investigated range. The obtained I-V characteristic curves for the investigated samples are typical for memory switches. The switching voltage increases linearly with film thickness in the range (113-750 nm), while it decreases exponentially with temperature in the range (303-393 K). The switching process can be explained according to an electrothermal process initiated by Joule-heating of the current channel. Measurements of transmittance and reflectance in the spectral range (400-2,500 nm) are used to calculate optical constants (refractive index n and absorption index k). Both n and k are practically independent of film thickness in the investigated range (149-691 nm). By analysis of the refractive index n the high frequency dielectric constant epsilon(infinity) was determined via two procedures and was found to have the values of 9.3 and 9.15. Beyond the absorption edge, the absorption is due to allowed indirect transitions with energy gap of 1.46 eV independent on film thickness in the investigated range.