Abstract Terbium gallium garnet (Tb3Ga5O12, TGG) transparent ceramics were synthesized by the co-precipitated method and vacuum sintering with MgO as sintering aids. Samples sintered at 1500 °C, 1550 °C and 1600 °C for 20 h were utilized to examine the phase compositions, optical quality, microstructure and magneto-optical property. X-ray diffraction (XRD) results show that the three samples have pure garnet crystal structure. The sample sintered at 1550 °C shows high transparency and the optical transmittance is close to 80% in the region of 500–1500 nm. SEM micrographs demonstrate that the sample sintered at 1550 °C exhibit best microstructure and the average grain sizes were 5.32 μm. The Verdet constant of the samples were investigated in detail at different wavelength and temperature. The results indicated that TGG ceramics can meet the demand for magneto-optical devices in the visible-near infrared region.