The low heat transfer and high energy storage performance of phase change material (PCM) will improve the thermal performance of the PCM-glazed units. However, decreasing the heat transfer results in uneven thermal load on the surface of the PCM-glazed units, which is an important cause of thermal stress in such units, because the glass in glazed units is a fragile material, and then large thermal stress can result in cracks and possible fallout of the glazed units. To study the thermal stress distribution of PCM-glazed units, a method combined numerical simulation and experimental analysis was conducted. First, the heat transfer performance and thermal stress distribution of PCM-glazed units with PCM thicknesses between 3 and 11 mm were experimentally investigated. Results showed that the thermal performance of a glazed unit was improved by adding PCM, and the variation of thermal strain on its surface with a PCM-layer thickness of 7 mm was the smallest in five test facilities. Then, the thermal stress was numerically investigated regarding the PCM height and the aspect ratio of the PCM-glazed unit. The higher the PCM height, the greater the maximum strain. An aspect ratio of PCM-glazed units of 1.5 was recommended.