This study aims to investigate the acoustic effects of thermal aging on partially reticulated polyurethane (PU) foam. An accelerated test was performed under appropriate test conditions as determined by thermal analyses of the material. Measurements of the absorption coefficient showed that the performance of the partially reticulated PU foam can be significantly reduced by thermal aging. The transport parameters were evaluated to analyze the origin of this change in the absorption behavior. Sensitivity analyses revealed that a decrease in the static airflow resistivity had the greatest effect in terms of reducing the absorption coefficient owing to thermal aging. In addition, observation and characterization of the microstructure of the aged foam to determine the root cause of this acoustic degradation indicated that heat-induced damage to the membrane was the most important factor. To verify this assertion, a periodic unit cell model that mimicked the topology of the cellular structure was constructed, and the mechanism responsible for the change in the acoustic behavior was simulated. The results presented herein can be used as durability guidelines for maintaining the performances of partially reticulated PU foams that are employed in high-temperature environments.