The effect of the sintering atmosphere on the structural, electrical, and luminescence properties of gallium oxide ceramics was studied using X-ray diffraction, scanning electron microscopy, luminescent spectroscopy, and electrical conductivity methods. A single β-Ga₂O₃ structure was confirmed by X-ray diffraction. The sintering of ceramics in the argon atmosphere caused structural changes on the surface and an insignificant increase in intrinsic volume. These features were also confirmed by scanning electron microscopy, where a larger number of vacancy-type defects were observed for argon-sintered ceramics rather than in the case of sintering in an oxygen atmosphere. The β-Ga₂O₃ ceramics exhibited three photoluminescence excitation peaks located at 3.33, 4.52, and 5.3 eV. The emission spectra revealed a broad peak in the 2.0–4.0 eV region, with a maximum at around 3.03 eV. The sintering atmosphere also affected the relative intensity of elementary luminescence bands. The photoluminescence properties are mainly attributed to the radiative recombination of charge carriers through donor–acceptor pairs. It was established that the electrical conductivity of ceramics also strongly depended on the sintering atmosphere.