A post-occupancy study was carried out to investigate the thermal environment in a high-standard office building certified by China Three-star Green Building Label. The study included a subjective evaluation of the indoor environment quality and work performance. A total of 182 office workers responded to the questionnaire survey based on the Building Use Studies (BUS) Occupant Survey and Reporting Method. Objective measurements of the thermal environment (temperature and relative humidity) under mechanically and naturally ventilated conditions were also carried out in the building. Although the thermal environment satisfied the majority of respondents, 12% and 20% reported dissatisfaction with summer and winter temperatures, respectively. The complaint on summer temperature was mainly from those working close to the chilled air outlets of the air-conditioners. The perception of cold winter temperatures revealed the potential shortcomings of sustainable building design in humid subtropical climates, where natural ventilation and passive cooling would predominate in the sustainable design while cold air in winter would tend to be neglected. The purpose of this study was to investigate the reasons why green buildings succeeded or failed to meet occupants’ perception and this could have an implication in the design decisions for green building practice.