The synthesis and characterization of thermally stable cyclotriphosphazene-based hybrid organic-inorganic blue-light-emitting polymers were reported. Monomers 2,4-di(4-bromoaryl)-2,4,6,6-tetra(phenoxy)-cyclotriphosphazene (3 and 4) and 2,4-di(4-bromoaryl)-2,4,6,6-tetra(ethoxy)-cyclotriphosphazene (7 and 9) were prepared beginning from hexachlorocyclotriphosphazene through a two-step reaction with the corresponding sodium 4-bromo-aryloxides. Next, 3, 4, 7, or 9 readily underwent a Suzuki cross-coupling reaction with suitable 9,9-dialkylflourene-2,7-bis(trimethyleneborate)s to afford the corresponding polymers. The structures and properties of the polymers were investigated by thermogravimetric analysis. differential scanning calorimetry, X-ray diffraction, and UV-vis and fluorescence spectroscopy. All polymers emitted blue light with high quantum yields. Subsequently, the thermal effect on the optical properties of the polymers was studied, revealing that the introduction of particular hybrid organic-inorganic three-dimensional cyclotriphosphazene in the polymer system prevented from aggregation of the polymer chain, enhanced thermal stability, and thus suppressed the undesirable green emission. On the basis of these studies, light-emitting polymer-based diode devices were fabricated.