Luminescent mesoporous Tb(OH)3@SiO2 core-shell nanospheres were synthesized through W/O microemulsion process at ambient temperature. The negatively charged silica favors a coating of the positively charged Tb3+ composite. Thus, silicon layer was adsorbed on the surface of Tb(OH)3 groups to form Tb-O-Si through electrostatic interaction. X-ray diffraction, field emission transmission electron microscopy (FE-TEM), energy-dispersive X-ray spectrometry, and Fourier transform infrared, UV/Visible, and photoluminescence spectroscopies were applied to examine the phase purity, crystallinity, surface morphology, and optical properties of the core-shell nanospheres. The FE-TEM results have revealed typically ordered mesoporous characteristics of the material with monodisperse spherical morphology in a narrow size distribution. The luminescent mesoporous core-shell nanospheres exposed remarkable splitting with broadening in the emission transition 5D4 → 7F5 (543 nm). In addition, the luminescent mesoporous core-shell nanospheres emit strong green fluorescence (from Tb3+) in the middle of the visible region under 325 nm (3.8) excitation. The luminescent mesoporous Tb(OH)3@SiO2 core-shell nanospheres can therefore be exploited as fluorescent probes in biomarkers or biolabeling, optical sensing, and drug delivery system. Further, these nanospheres could have potential use as scattering layers in dye-sensitized solar cells.