Cerium-doped gadolinium–gallium–aluminum garnet (Gd3Al2Ga3O12:Се3+, GGAG:Се) is a promising scintillating crystal. This new material was synthesized for the first time in 2011 [1], and nowadays it is characterized by the extremely high light yield for the scintillators based on the complex oxides - up to 46000 ph/MeV [2]. The crystal structure of GGAG belongs to the cubic system, space group Ia3d. It is non-hygroscopic, and it has high stopping power. Such properties allows to consider the GGAG:Се crystals for the application in various highly demanded areas including radiation monitoring and medical imaging. However the origin of the high light yield is not clear so far. Moreover an analysis of the literature data shows that some fundamental characteristics of this material, in particular the refractive index, have not been measured. Thus, the purpose of this study was to determine the optical and the luminescent characteristics of GGAG:Ce crystals.   GGAG:Ce crystals were grown at “Fomos-Materials” Ltd. by the Czochralski method on an upgraded Kristall-3m set-up. The initial material for growth was a stoichiometric charge prepared by solid-phase synthesis from a mixture of initial oxides of 99.99% purity grade. The crystals were grown from an iridium crucible 80 mm in diameter in a mixture of argon with 1–2% oxygen.   The spectral dependences of the absorption and reflection coefficients of GGAG:Ce were obtained under normal incidence of naturally polarized light in the wavelength range of 250–800 nm using the UV-Vis-NIR spectrophotometer Cary-5000 (Agilent Technologies) with the accessory “UMA”. Luminescence and excitation spectra were measured using a deuterium D 200 VUV lamp at T = 79 К. Shamrock 303i (Andor Technology) was used as a secondary monochromator and luminescence has been detected using a Hamamatsu H8259 photon counting head.   The broad non-elementary emission band with a maximum at 530 nm was observed and ascribed to 5d-4f electron transitions in Ce3+. The reflectance and transmittance spectra were measured for p and s-polarized light in the wavelength range of 300–800 nm at the angle of light incidence 10º– 75 ° with a step of 5°. Based on these data, the spectral dependences of the absorption coefficient were calculated taking into account the reflection. Three absorption bands were detected in the absorption and luminescence excitation spectra. The bands at 420–460 nm and 340 nm are ascribed to Ce3+ while the band at 270 nm arise due to electron transitions in Gd3+.   Two spectrophotometric methods were used for obtaining the refractive indices: (1) definition of the Brewster angles and (2) measurements of the reflection spectra from one surface at the angle of incidence close to normal [3]. As a result we have calculated the refractive indices, plotted the dispersion dependence, and approximated the experimental data using the Cauchy equation [3].