Two new terbium complexes with aromatic carboxylic acids, [(Tb)2(L1)6(H2O)4] (1) and [(Tb)2(L2)6(H2O)2(DMF)2] (2) (HL1: nicotinic acid; HL2: 4-hydroxybenzoic acid), with different coordination geometries have been synthesized and their crystal structures determined. The luminescence properties of the two complexes, including the phosphorescence lifetime, have been investigated. The effect of a secondary ligand on luminescence of the ternary terbium complex with carboxylic acid and the relationship between luminescence properties and crystal structure, including coordination mode of the carboxyl groups from HL1 and HL2 and coordination mode of a secondary ligand, are discussed.