Thermally Activated Building System (TABS), which is embedded water based heating and cooling system, has been applied to many energy-efficient building such as airports, convention centers, and large office buildings. TABS can reduce a peak load due to the time-lag effect caused by a high thermal inertia of the concrete construction, where a heating or cooling pipe is embedded. It can also improve energy efficiency of buildings because it can be integrated with low temperature heating and high temperature cooling heat sources such as geothermal energy. Also it was known that radiant heating and cooling system improves the indoor thermal comfort condition. However, there are few existing cases and researches of TABS under the weather condition of South Korea, which is hot and humid in summer, and cold and dry in winter. Therefore, it is necessary to have a basic thermal performance and occupants' thermal comfort data of TABS. This study focuses on the evaluation of TABS in the view of occupants' thermal comfort by analyzing of the comfort criteria with TABS in campus building of South Korea. To achieve this purpose, on-site measurement and field survey were conducted in summer and winter, respectively. The building was completed in 2008 and the pipes of TABS were embedded in concrete slabs. The surfaces of the ceilings are used heating or cooling surfaces, which total area is about 9,000 m2 (96,875 ft2). The surface temperature of the ceiling, vertical air temperature, mean radiant temperature, relative humidity, and air flow velocity were measured. Using these data, the predicted mean vote (PMV) and predicted percentage of dissatisfied (PPD) were analyzed according to ASHRAE 55-2004. Furthermore, the thermal sensation votes (TSV) and comfort sensation votes (CSV) of occupants were examined by the questionnaire in summer and winter, respectively. The results of this study were provided as the base data for application and operation TABS in building.