The effective magneto–optical properties of novel nonanuclear Tb(III) complexes with Tb–O lattice (specifically, [Tb9(sal-R)16(μ-OH)10]+NO3–, where sal-R = alkyl salicylate (R = −CH3 (Me), −C2H5 (Et), −C3H7 (Pr), or −C4H9 (Bu)) are reported. The geometrical structures of these nonanuclear Tb(III) complexes were characterized using X-ray single-crystal analysis and shape-measure calculation. Optical Faraday rotation was observed in nonanuclear Tb(III) complexes in the visible region. The Verdet constant per Tb(III) ion of the Tb9(sal-Me) complex is 150 times larger than that of general Tb(III) oxide glass. To understand their large Faraday rotation, electron paramagnetic resonance measurements of Gd(III) complexes were carried out. In this Report, the magneto–optical relation to the coordination geometry of Tb ions is discussed.