Abstract Glazing units are important for providing passive solar gain and air ventilation in buildings, but their thermal performance is very poor compared to other building components, which results that energy loss from building envelope becomes much more drastic when the glazing area is large. Incorporating phase change material (PCM) in the glazing unit is an effective approach to increase its thermal performance. The glazing unit containing PCM can absorb part of the solar radiation for thermal energy storage while letting the visible radiation enter the indoor ambient for daylighting, which results in reduction of the temperature fluctuations and improvement of the thermal comfort of indoor occupants. A lot of researchers investigated optical and thermal performance of window systems containing PCM in buildings. However, there is a lack of published research review including numerical methods of optical and thermal performance and physical parameters of PCM used in the glazing units, especially for the optical performance of glazing units containing PCM. The present work reviews the experimental and simulation researches on the optical and thermal performance of glazing units containing PCM and discusses the employed research methods, mathematical models and important conclusions drawn. Finally, the challenges and future works of glazing units containing PCM are addressed.