Scintillation materials capable of transforming absorbed high-energy particles into visible radiation photons find multiple applications including advanced medical visualization methods. Gd3Al2Ga3O12 : Ce is a promising oxygen-containing sсintillator for fabrication of detecting crystals of positron emission tomographs due to its unique properties, e.g. high density, high light yield, radiation hardness etc. However its kinetic parameters currently restrict its use in this field. Attempts at improving the luminescence rise and decay time kinetics by introducing additional impurities have become a top priority task for many researchers. Analyzing literary data one can conclude that the optical parameters of co-doped crystals have been studied insufficiently or have not been studied at all. We have studied Ca2+ and Zr4+ co-doped Gd3Al2Ga3O12 : Ce single crystals by optical spectroscopy in the 200–2200 nm. We have taken the optical transmittance, absorption and reflection spectra and measured the refractive indices. Dispersion curves have been obtained by approximation of experimental refractive indices using the Brewster method and the Cauchy equation. Material constants of these equations have been estimated for each of the co-doped crystals.