Buildings account for a large amount of global CO2 emissions, consumption of natural resources, and deterioration of ecosystem due to the expansion of land use. Under the pressure of reducing impacts of buildings on the environment, green building rating tools have been developed to provide frameworks for high-performance building designs and practices based on the three pillars of sustainability: environment, society, and economy. Certified green buildings are expected to achieve high performance in energy efficiency, occupant satisfaction, and have lower operating costs. However, during the occupancy phase, there are many factors that cause changes in buildings such as technical issues, users’ behaviors, or social and economic situations. Thus, the real performance of green buildings is not always as good as it is shown in the design phase. In reality, very few buildings conduct a post-occupancy evaluation to assess building performance, and evaluate the effectiveness of changes in buildings, from occupants’ perspective. There-fore, this thesis conducted a post-occupancy evaluation survey in a certified green build-ing, Kampusareena in Hervanta Campus, Tampere University, to (1) evaluate the build-ing’s performance in terms of physical features and indoor environment quality and (2) occupants’ satisfaction with additional new energy-saving measures, to further improve the efficiency of building performance. The results showed that the green building’s phys-ical features had high recognition among users and therefore, connected to the occu-pants’ experiences in the building. In terms of indoor environment quality, occupants were more satisfied with the overall comfort and thermal comfort in the green building than in other campus buildings. However, they felt no differences in the remaining ele-ments between the green building and other conventional buildings. Lighting and noise level received many negative responses, especially from the university staff, which may require improvements in the future. Additionally, the new energy-saving measures ap-plied in the building, which were the reduction of indoor temperature and water flow rate, did not have much effect on the occupant’s comfort. These measures also received a lot of support for their continuation in the future.