The thickness of the lubricating film plays a vital role in the operational efficiency and reliability of rolling bearings. Ultrasonic reflection techniques offer a promising noninvasive approach for the in situ evaluation of lubricant films. However, accurate identification of the central film thickness remains challenging because of several complex factors, which include dynamic fluctuations, localized elastic deformation, cavitation effects, and variations in the oil supply. In this study, a comprehensive theoretical and numerical framework for elucidating the effects of these factors on ultrasonic wave propagation in lubricated contacts is presented. Numerical simulations in which the elastohydrodynamic lubrication (EHL) regime and cavitation-induced effects are considered are carried out to obtain surface deformation profiles and identify cavitation regions. High-fidelity acoustic simulations are subsequently conducted to interpret the reflected ultrasound data. The reflection coefficient distribution exhibits a symmetric ‘‘double peak with central valley” pattern that is induced by the combined effect of the contact geometry and the EHL-induced oil film thickness distribution. Cavitation causes the central valley to shift toward the inlet region and increases the reflection coefficient. Accordingly, the central film thickness is extracted from the distribution of the reflection coefficient under different operating conditions. Experimental validation using both glass–oil–steel and steel–oil–steel bearing setups confirms the effectiveness of the proposed method. The high-resolution fluorescence measurement that is adopted in the glass–oil–steel configuration validates the simulation of the reflection coefficient distribution. Furthermore, theoretical EHL calculations are performed for the steel–oil–steel configuration to validate the measurement accuracy for the central oil film thickness.