This work examines the synthesis and characterization of crack-free, β-Bi2O3 thin films prepared on Pt/TiO2/SiO2/Si or corundum substrates using the sol-gel method. We observed that the Bi-based precursor has a pronounced influence on the β-Bi2O3 phase formation. Well-crystallized, single β-Bi2O3 thin films were obtained from Bi-2ethylhexanoate at a temperature of 400°C. In contrast, thin films deposited from Bi-nitrate and Bi-acetate resulted in non-single Bi2O3 phase formation. TEOS was used for the stabilization of the β-Bi2O3 phase. The phase composition of the thin films was characterized by means of X-ray diffraction (XRD), whereas the morphology and thickness of the thin films were studied using scanning electron microscopy (SEM). The β-Bi2O3 films' dielectric properties were characterized utilizing microwave-frequency measurement techniques: (1) the split-post dielectric resonator method (15 GHz) and (2) the planar capacitor configuration (1–5 GHz). The dielectric constant and dielectric loss measured at 15 GHz were 257 and 7.5 × 10−3, respectively.