The Tb-Mn-Ga system has been investigated at 870/1070 K by X-ray powder diffraction and microprobe elemental analyses. The existence of the known compounds Tb2Mn11.7-15Ga5.3-2 (Th2Ni17-type), Tb2Mn10.2Ga6.8 (Th2Zn17-type), TbMn5.4-4.5Ga6.6-7.5 (ThMn12-type), Tb2Mn0.3-0.7Ga6 (K2PtCl6-type), TbMnGa (ZrNiAl-type), Tb2MnGa3 (CeCu2-type), TbMn0.26Ga1.74 (CaIn2-type) and quasibinary solid solutions ThMn12-type TbMn12-10.9Ga0-1.1, MgCu2-type TbMn2-1.4Ga0-0.6 and AlB2-type TbMn0-0.2Ga2-1.8 has been confirmed in the Tb-Mn-Ga system at 870/1070 K. The appreciable solubility of other binaries was no observed in the Tb-Mn-Ga system. The K2PtCl6-type Tb2Mn0.5Ga6 compound shows mixed ferro-antiferromagnetic ordering with high-temperature ferromagnetic ordering (TC) of 28 K and antiferromagnetic transformation of magnetic ordering (TN) at 20 K.