The results of studies of the electronic structure and optical properties of intermetallic compounds GdFeAl and GdFeSi are presented. The spin-polarized densities of electronic states and interband optical conductivity spectra are calculated using the DFT+U method, taking into account the influence of strong electronic interactions in the 4f-shell of Gd. The optical properties of these materials are studied by ellipsometry in the wavelength range 0.22–16 μm. The nature of light absorption is discussed on the basis of a comparative analysis of experimental and theoretical spectra. It is shown that the calculated densities of electronic states makes it possible to interpret qualitatively the main features of the frequency dependences of optical conductivity.